It looks like you are doing Hybrid Autopilot join which is not recommended anymore by Microsoft. Consider the scenario you would have only cloud-joined devices.
But to solve the actual problem, I think steps are;
- Make sure you can join computer into Active Directory domain manually in that network.
- Make sure that the connector is working from Intune to AD.
- Make sure that credentials used in connector have enough rights to join device to domain
- Make sure that the OU location is specified as distingueshed name in Domain Join policy in Intune.