Try plugging it in and leaving it for a night, then, try using a different power cord, if it takes AC directly.
Sometimes you have to sort of “push and pull” the cells to get them to start taking a charge again.
sealed lead-acid batteries are practically bullet proof.
but if nothing works, gotta crack it open, and change the cell - find a electronics parts store’ - they will give you a reasonable price for the battery - Also remember you can sometimes join 2 batteries together to make the final voltage you need, if you want to Frankenstein it. like if it needs 12v - and you can only find two-6v cells, as long as the amperage is the same or more then they can be joined using a pigtail, i did this for mine a while ago. BUT you would need to read up on doing that properly to not cause a meltdown.
errrrr, you can check the fuse with a meter :)