Ubuntu 20.04 LTS doesn't wake from suspend by keyboard or mouse, only by power button on my desktop machine

I have had a laptop running 16.04, then 18.04 and now 20.04. It has always resumed from suspend on hitting a key or the touchpad.

I have recently got sick of Windows Vista on my desktop machine and added a bit more RAM and replacement hard disk and installed 20.04 on the machine as the only OS. Once put in suspend mode, only pressing the power button momentarily wakes the machine up. When suspended, there is no visible indication that it is in that state, as opposed to completely powered off.

Is there any way I can change these two aspects of suspending the machine?

By way of additional information, the desktop machine is as folows;

The machine is an Advent QC5003 with an Intel® Desktop Board DG45ID as
a motherboard. Of the 6GiB of memory ,most is free

free -h shows
              total    used   free   shared  buff/cache   available
Mem:          5.7Gi    1.8Gi  1.9Gi  284Mi   2.1Gi       3.4Gi
Swap:         2.0Gi    0B     2.0Gi

sudo dmidecode -s bios-version
IDG4511H.86A.0090.2008.0924.1800

Update, 9/10

Having had a root around in the BIOS settings, I was optimistic that changing the ACPI state from S3 (low power) to S1 (more components powered) would solve the problem. Sadly I was mistaken, as when it’s suspended to S1, the light around the power button remains on and I can hear a fan turning but the keyboard and mouse will not move the machine to a resumed state. Even the Numlock and caps lock keys don’t change the keyboard LEDs. The ability to suspend is of limited use for a desktop machine powered by the mains, so this problem remains as a non-urgent anomaly in my mind.