My multisite was fine yesterday (24 hours ago) and in between I havent done anything new or that I shouldnt have ie new installation of plugins/themes etc.. In fact I havent done anything major for a 4/5 days now at least, maybe a week.
Today, all multisite users have lost access to their sites and are not listed in multisite admin as being associated to their sites. If I manually add a user to a site, I get the yellow "User added" message at the top of the page, but they are not added eg I added the user "paul" to the site "paul" and its not there and paul cannot log in to the site but gets the global dashboard instead like a standard user only account. I cannot even add the superadmin to the user list which appears to be completely blank.