Admins don't include Office 365 Group Owners

It's most likely going to be someone overwrote all the site collection admins of the sites and they don't have the owners group set as site collection admins?

You should either be able to go to site collection admins in the site itself if you have access, or run powershell get-spouser -site "Siteurl" | fl and check for the group in there and IsSiteAdmin should be true on the owners group. If not then we need to set that using set-spouser -site "siteurl" -LoginName guid -IsSitecollectionadmin $true guid being the guid of that group.

You might be able to script using the IsGroup property to find the groups where the name includes Owners but it could get complicated to do for all sites, but forall looping and looking for something like that might work, you should be able to write a select for all the owner groups and export to csv and audit it, if it looks like it would be the right groups then you can then take that query and then you can use set-sposite command with similar filters and make all those groups sitecollection admins. I'm no powershell expert, but it goes something like that, but it'll take some work to figure out.