This is a new bug that started popping up in A20.1. It appears that the game is have trouble determining where your player is supposed to spawn and can’t resolve the issue. Unless someone else has come up with an easy fix, I haven’t heard of any, you need to delete your player profile then try to load back in. If you fail to get in after deleting the profile then the entire save is corrupted. If you do get in, you’ll be level one. You can then give yourself xp to get your levels back and use the creative menu to get your items back. Your base and all of your stuff in boxes will still be there, you will need to find it as your spawn will be random the first time. Hope this helps.