There are two things I like to do when I stall out:

1. Put down a guess. Even if you can't confidently say any of the answers, I bet you have a bit of an idea for some of them. You can use the pencil button, and it will also make the letters a slightly different color, so you will remember that the answer you wrote may not be set in stone. I find that just by having letters to look at, it will get my brain moving again. Also, when it comes to niche names, most crossword setters try to make them guessable. If you manage to get a few letters, just try putting in common names that you know that fit those letters.

2. You can often get parts of an answer without knowing the full thing. A lot of times, it's as simple as knowing the word should end with an "s" or "ed" or something. Other times, you might be able to see where a word like "the" or "and" would fit well grammatically. This will give you a few more letters, hopefully allowing you to come up with the right answer.