Weird issues out of nowhere - Support Needed

Technicians are getting the following error when creating tickets:

They choose the requester, whose associated to his site, and his information is autopopulated. No problem creating the ticket... But once the page refreshes and we're redirected to the created ticket the error quickly pops up and the Site field isnt populated - it says "Not associated to any Account". We verified the configuration of the Sites in Accounts and nothing has been changed, everything was working fine until today. Requesters have sites associated to them, Sites are associated to Accounts, everything in the configuration is untouched and was previously working.