It’s still a relatively thin coat, and hard to say anything without seeing it in the flesh.

Did it go on over a stain or something like Dingotone? If the latter, then the finishes may not be 100% compatible and one is stopping the other from going fully hard.

But it may just be that the body wood is soft and a thin layer of poly can only provide so much support and strengthening. If you want a thin finish, then it’s not going to be as hard-wearing as a thicker finish would give.

I’ve got no experience with that product, so can’t suggest anything more definite.