There are a few reasons for this restriction in Airtable:
Permissions Level: You need creator/owner permissions to add apps to your base. The error could mean you only have the access level of Editor, Commenter, or Read-Only.
Enterprise: Some companies block users from installing 3rd-party apps on the marketplace. If you're on an Enterprise plan, your admin needs to enable this feature to allow you to install apps from the Marketplace. In case it's disabled, you would need to reach out to your account manager or Airtable Support for help.
Similar Name: double-check that the selected workspace is in fact the correct one when installing the app (especially if you have multiple workspaces with the same name).
💡If it's not possible for you to install the Sync App or the scripting app, we do provide another way to sync your base using only Airtable API. But it comes with some limitations.