Audio Midi Setup - can't open midi studio

I am hoping someone can please help me with an urgent problem! I am having trouble using Midi with my mac.

Midi devices are not being detected by the computer.

When I try to open the Midi Studio window, it takes a long time for anything to happen, before eventually I get a message saying "The MIDI Server can't be opened".

Following advice on this and other forums I have tried to trash the MIDI preferences (com.apple.audio.AudioMIDISetup.plist), I have deleted all Midi drivers including those revealed by opening Terminal and typing the following:

kextstat -kl | awk ' !/apple/ { print $6 $7 } '

(as per this thread https://www.gearslutz.com/board/music-computers/1248576-cannot-open-midi-studio-mac.html)

I have tried unplugging all peripherals and restarting multiple times.

I use Midi every day for my job and am completely stuck without it!

I have read that one option is to erase the disc and reinstall OS, but I want to avoid this if possible in case I were to lose anything along the way.

Any help greatly appreciated!

Thanks,

Hugh

iMac Pro (2017) 10.13.6, Focusrite 18i8 2nd gen