You are likely to have a locked bootloader and stuff stored on your phone.
I added the hashtag fp4 to your OP. There have been a surprisingly large number of people have reported same or similar.
I suggest you review the other similar cases by hashtag. The main choice would be do you prefer to do
- a clean fresh install and rely on your own backup, or
- still be sure you have a good backup and attempt a dirty upgrade as has been attempted with mixed success by others.