I'm currently a 1600 USCF with a tactic rating on chesstempo.com of high 1600. My chess.com tactic rating is 1600 as well. Though my best tactic rating has been high 1700 on chesstempo.com. The problem is that my tactic rating always oscillates between 1600 and high 1700. I can never reach higher tactical levels than 1700. I practice 30 minutes of tactics every day as my chess coach recommended. However, I haven't seen any improvement. Any advice to raise my tactic rating to 2300+?
As noted in the comments, 2300+ tactical ability is a ridiculous goal to aim for, if your current level is 1600-1700. This will only lead to disappointment on your part, as improving your tactical level to 2300+ will probably mean that you will have to raise your overall playing strength by maybe 300-400 rating points. This takes years to accomplish, unless you have lots of time, resources and talent, in which case it will probably still take at least a year.
A suitable primary goal is instead to raise your tactical level by roughly 100 points. Depending on your situation, this can be done in a few weeks. However, just doing tactics problems on problem sites will not accomplish this very efficiently. Exercises are good, but not doing anything else will not improve your play by much.
I suggest you read a good book about tactics if you haven't already. One that I enjoyed very much was "Understanding chess tactics" (I think later editions of the book is called "Chess tactics from scratch") by Martin Weteschnik, containing many good examples and clear explanations of themes. However, it's not the only good tactics book, and if you have a chess coach, that person may have some suggestions on what to read.
You'd probably also want to play against strong opponents (1800+ at your level), as they're very likely to be better than you tactically. This will be good for your overall play and toughness at the board, which goes hand in hand with tactical ability.
My advice is, and it worked for me, prioritizing quality over quantity.
For every problem spend as much time as you need. Try to find out one or more tactical motifs in the position to guide you in your guessing. If you haven't, read the tactical motifs help page before.
Once you find the tactical motifs, note them down and start thinking in how to get advantage from them; look for intermediate moves (yours and from your opponent), and all possible responses. Exhaustivity is even more important than depth, most times you'll fail a problem because you miss a move than because you didn't think deep enough.
At first it will take you too much time to solve every problem: that is good. As you practice you'll be able to recognize patterns faster AND to solve harder problems.
Doing the opposite (trying to solve the problems the faster the better hoping that you'll learn to do it better by repetition) won't help you.
2300 is a lofty goal, but I'll humor you. You need to progress with baby steps. Also, 30 minutes a day is nothing. Perhaps you need more practice a day. Now, you said you were high 1600s, but I'll assume 1700 for an easy number to crunch. This means 600 point of improvement, and this will make you a tactical master. You are probably miles away from a master, which is okay, and must take this slowly.
Here are some tricks to help make you very strong in a year, assuming you commit yourself religiously. This did work for me. I am only rated 1539 because I haven't done tournaments in a while, but I learned how to consistently draw/beat 2100s easily, because I played several skittles games and nonrated events at camps, my tactics in standard on chess tempo are well above 2000, and I've met people with the exact same story (except they are more active than I in tournaments). Plus, you have coaching experience, and I don't. You have an advantage that I don't have, so I think you can do it too.
Discipline. Mastery is a commitment. It takes long working hours, a lot of homework, and a strict critic, which is yourself. Buy yourself complex endgame books, like that of Jesus de la Villa or Mark Dvoretsky. Purchase Think Like a Grandmaster by Alexander Kotov to boost tactics even further and learn how to analyze complexities properly. Now, at 1600, these books are tricky, but they hold everything you need for mastery except maybe opening knowledge, which is more crucial than some think. You just need to harness it, and you can do that with tactics. Read these books front to back, and you will see significant improvements, but be sure to read it for content. As with tactics, I'd recommend two hours a day. At this point, tactics matter most (arguably).
Projections. If you are like me, you like numbers, and chess tempo offers great opportunity for that. Set a criteria daily, weekly, and/or monthly/bimonthly as to how much comprehensive studying you want to get done within these time periods. Daily schedules are the most important. Want to be 2300 in a year? 600 divided by 365 is 1.643..., which should be paired by your side goal or two hours a day, meaning you still need to practice that long a day, but you want to be that many points higher. So, day one you are 1700 and you mess up and drop to 1690 after two hours. The goal was 1702 today (I'm rounding to 2) and the day is done. Tomorrow is 1704. What now? Well, I hope you know why you got these problems wrong, because you're shooting for 1704 tomorrow. This doesn't seem like a whole lot, and it isn't. The point is you can still, at this rate, make it to 2300 during your year, and you also have the time to absorb the knowledge from every level. As with reading, read maybe 10 pages of endgame a day with 10 pages of middlegame theory or book tactics, like Think Like a GM by Kotov and a constant stream of opening patterns and theory in your favorite openings, which I won't really focus on.
Practice playing somebody frequently who beats the crap out of you all the time. Analyze your games on chess.com and figure out your mistakes you that you don't make similar ones again.
For me, I used an engine, which is a great resource. Try stockfish, because it's cheap and easy to get your hands on it. I used an app called Chess Tiger, in which the computer is rated 2790 FIDE, apparently, on its max level, but it's not reliable and is frankly a bad engine.
I played chess with this thing so much it can't beat me anymore, but draws. This does not mean I'm a good player. It just means I figured out how to counter a predictable playing pattern from a lousy engine.
But the benefits are great! You learn how to go down with a massive struggle and play brilliantly to the endgame, where things get most interesting. Plus, you learn how to think like that computer, which is a venomous weapon employable on the chess board. Play serious chess with it, though, thinking long periods of time just like if it was a human on OTB. You may not be able to beat it, but getting the crap beaten out of you teaches you how to defend yourself. Maybe you'll beat your first grand master someday!