I can't unarchive the main site

I’ve recently updated the plugin after not having updated it for about two years (lost contact with that client) and suddenly the main site is archived and I can’t unarchive it (the option for unarchiving is not there). The subdomains work fine and I can see the main site in backend but visitors get a ‘This site has been archived or suspended.’
What could the problem be? I also tried to add the main site again and get a ‘Missing or invalid site address.’

https://www.ads-software.com/plugins/wordpress-mu-domain-mapping/