My Lisa 2/10 has had its IO board replaced so it has A8 ROMs.
A 2/10 I/O Board normally has an 88 ROM. If one puts an A8 ROM in a 2/10 I/O Board (ie. mismatch the I/O ROM and the I/O Board), the floppy won't work.
If the replacement board is a 2/5 I/O Board, then the A8 ROM is the appropriate match for the board, however, the 2/10 will be missing the Lite Adapter (which mounts in the drive cage of a 2/5), so the PWM speed signal to the floppy drive will be missing, preventing it from working.
To resolve this you could add the Lite Adapter between the Floppy Drive (FEMU) and the 20 pin ribbon cable in the Lisa 2/10 chassis. However, this is non-trivial as the Lite Adapter is designed for the 26 pin cable of the 2/5 chassis, so you will need to fabricate some kind of adapter/modification to use the Lite Adapter with the 2/10 chassis.
AFAIK, currently there is no posting for how to modify the Lite Adapter/cabling to use a 2/5 I/O Board in a 2/10 chassis (although there is a posting for how to modify the Lite Adapter to use a 2/10 I/O Board in a 2/5 chassis).
The 2/10 and 2/5 I/O Boards are easily distinguished by the larger chips at the top left of the board. The 2/10 I/O Board has three, the 2/5 I/O Board has two.
edit: I've assumed the FEMU needs the PWM signal, I've now realized that I'm not certain that is the case, but it seems a likely suspect for the problem.