Problem with startup

Fairly old Mac Intel my wife uses has been fine until yesterday. It normally loads up without asking for a password. Now, this happens.

Grey screen and progress bar as normal

Then, it displays her name and a password box

The keyboard (USB) doesn't input any letters

I have tried several times. Sometimes, the keyboard light flashes, and pressing the F1/F2 (brightness) keys inputs dots in the password box, but still no letters.

Also, I think it normally chimes on startup - it isn't doing that now.

I have tried unplugging the keyboard and using a bluetooth keyboard, but nothing.

I would be grateful for any help - thank you.