My Bluetooth keyboard stopped working with just one specific laptop. (acer aspire E5-771G-76QZ)
Laptop says it is paired but my keyboard his Bluetooth light lights up when pressing a button (this means it's not connected to anything).
so I tried the keyboard on other devices (laptop, desktop, phone) and it works just fine.
When trying to delete the keyboard from the paired devices, it "installs" it self when restarting the laptop, I even deleted my Bluetooth drivers and deleted all the files with iobit uninstaller, after restarting my laptop, Bluetooth was installed by it self again and the keyboard was "paired".
ps. I can pair my phone or other Bluetooth devices without any problem with this laptop, so it looks like it's a quarrel between the laptop and the Bluetooth keyboard.