I am running into an issue where our teams calendars are disappearing from Outlook. These are the primary Team Groups that are created. I add it to my Outlook they are there for about 5 minutes, then they disappear. OWA just sates I don't have the correct permissions to add the groups. I have make sure caching is on (1 year), set -HiddenFromExchangeClientsEnabled:$false -HiddenFromAddressListsEnabled:$false in Powershell. Regular Office 365 Group calendars work just fine.
It might take some time for the changes you made to take effect, I'd suggest also checking via OWA. If the calendars are not accessible there too, you can redo the PS bit, or open a support case and report this.