Just in case anyone has a relative modern Gigabyte AM4 motherboard and is having trouble getting wakeup functionality working ensure you have the following BIOS settings.
My problem was I had stopped using wakeup functionality and had updated my BIOS in the meantime. When I tried to use wakeup again it was not working. ErP was a new BIOS option that defaults to enabled it must be set to disabled for wakeup functionality to work.
Enter BIOS - Settings - Power Platform
- ErP - Disabled (this is a newish option - having this enabled causes most wakeup functionality to stop working due to it enabling saving a couple more watts - set it to disabled)
- Resume By Alarm - Disabled (although it sounds wrong this must be set to disabled - it does not work if you set this to enabled)
- High Precision Timer/ HPET - On my system this works on either enabled or disabled but it is commonly known that if you have problems set to disabled