Hi Engineering IOT,
Greetings & Welcome to Microsoft Q&A forum! Thanks for posting your query!
It looks like you have already assigned the AcrPull and Contributor roles to both your ML Workspace and batch endpoint managed identity. However, the issue may be that the compute running the job does not have a Managed Identity assigned or lacks the necessary permissions to pull images from Azure Container Registry (ACR). To resolve this, please check if your compute has a Managed Identity.
If no identity is assigned, you can enable a System Assigned Managed Identity Once assigned, grant the compute’s identity the AcrPull role on ACR. After making these changes, restart the compute to ensure the new permissions take effect.
For more information: Azure Container Registry without admin user
I hope this information helps.