If you are having trouble using an add-on after downloading and restarting your console, then the following options may help you.
How to Restore Game Licences
Game licences authorise you to play your purchased content on the console you are signed into with your PSN account.
- From the Home screen, open the main Settings menu.
- Choose Users and Accounts.
- Select Other.
- Select Restore Licences.
- Once complete, try downloading your Add-ons again.
How to Enable PS5 Console Sharing
PS5 Console Sharing and Offline Play is automatically enabled on the PS5 console you use to sign in to PlayStation™ Network for the first time.
- Go to Settings, Users and Accounts, Other, Console Sharing and Offline Play.
- Select Enable.
Your Add-Ons May Exceed the 64 GB Storage Space Limit
You can learn more about this issue and how you can work around it here: PlayStation 5 - 64 GB Limit on Add-Ons