Site crashed after loading plugin

Hi, I have installed 'global footer content' and now nothing works on my site! I get the following message if I try and go to any part of the admin: The Global Footer Content plugin is only compatible with WordPress Multisite.

I got an answer back from one of your colleagues to open a ticket, but as you can see, I have had to pay $49!

I need this sorting asap - my site has to be up an running in 2 hours please.