Enable keychain?

I am trying to rebuild my app and enable keychain but it won’t work due to the below.

By default the uploaded iPhone Provisioning Profile does not include the “Associated Domains” and “AutoFill Credential Provider” permissions. You will need to regenerate your iPhone Provisioning Profile after adding these permissions.

Please where can I find the guide to re-configuring with the above in mind?

I think you need to reconfigure your App Identifier and add permissions for Associated Domains and AutoFill Credential Provider. Read the bullet points in this article: Step 1: App Identifier - AppMySite

I would also recommend contacting support as they would be able to pinpoint the exact issue.