The identity specified in the Access Token does not have permissions to perform this operation.
Possible Causes
Sync's ACL control has been unintentionally enabled on your Sync service instance.
An SDK endpoint trying to read or write a Sync object does not have the correct permission configured.
The identity you specified in your SDK's token does not match the permissions that you intended for them.
Possible Solutions
Disable the ACL feature on this Sync service. This will allow access from any SDK with a valid token.
Do this by either unchecking the AclEnabled feature in the Twilio Console, or setting the acl_enabled flag to false via the Sync REST API.
Confirm a valid permission is configured via the Sync Permissions REST API, and that the configured identity matches the identity you provide in your FPA Access Tokens.