Explanation of the error
This error is surfaced by Salesforce when trying to relate or deploy directly to an object that you don't have permissions to access.
Salesforce explains in their documentation that this error:
"It happens when a user tries to use a Flow, save a record, or perform an action that depends on a connected record, but the user doesn’t have the required permissions to access that record.
This connected record is usually linked through a lookup field or a Master-Detail relationship. The user is attempting to use something (the connected record) they aren’t allowed to see."
Resolution
Check the permissions on the object you are trying to relate or deploy to, and grant permissions on the objects for the Salesforce user you are deploying as.
Further examples of this Salesforce validation error can be found here:
Disclaimer: This error is returned by Salesforce directly, rather than Gearset. Even so, we offer guidance based on our combined experience with the Metadata API. Where possible, we try to help guide you to fix or avoid this error. In the case that this isn't possible, we may need to direct you to Salesforce support for further clarification.