Everything should be working again but I managed to break everything quite badly today.
First I installed a new plugin which ended up causes a network-wide server error. I then disabled all plugins which was a bit of a sledgehammer approach. After I removed the broken plugin, I had to redo the network and site-specific activation.
I am 99% sure I have fixed everything that I messed up but if anything is wrong please do let me know.
This is an actual image of me working hard!
Anyway, back to the grindstone for me.