I have managed to update the firmware
One potential weak link was that I was using the cable from my EM1iii as recommended since I don’t have a USB-C port. I tried turning the cable round just in case with no luck and then downloaded OM Workspace on my husband’s laptop - lucky him! He has a USB-C port and is on Monterey.
I had to go into security settings, but this time the details were there for me to select under the General tab and everything went smoothly.
At some point I will try uninstalling and reinstalling Workspace on my laptop but I’m happy it’s sorted for now. Phew!
Thank you everyone for your input - and particular thanks to
@snerkler - offering to install it on your older laptop was so very kind and beyond the call of duty.