imac 2014 21 inch with Catalina doesn

Try again with a keyboard and mouse that are known to work otherwise.

Here's an Apple Support document with some keyboard troubleshooting tips.

https://support.apple.com/en-us/HT204540#usb

Maybe there's some help there.

If your Firewire or USB isn't recognizing any device.  A solution which has worked for some whose hard drive became invisible in 10.4 was simply to follow these four steps to reset the Firewire/USB bus:

1. Shut the machine down.

2. UNPLUG the power lead to the computer and any firewire/USB drive or devices.

3. leave it for 10 minutes.

4. Connect back up and reboot. 

http://www.macmaps.com/firewirebug2.html