I have an old Dell Bluetooth keyboard and mouse from an Inspiron (Y-RAQ-DEL2) which I use with various different things but mainly my other laptop which the kids use for homework.

It used to work fine but suddenly the other day it didn't auto connect so I went through the Win10 Bluetooth process and it paired ok but the next day when we went to use it again it had unpaired and now the Windows pairing was asking for a PIN??????

Looking on the support pages it says the PIN is in the manual but as mentioned these are old so we don't have the documentation any more.

The laptop can see both the keyboard and mouse but both refuse to pair because of a lack of PIN