AI Search Indexer will not create at all no matter what options I select?

Question

Trying to setup Azure AI Search service, following the initial wizard is fine, then go to the resource and import data, and every time fails on creating the indexer with the following error.

If I go to create the indexer afterwards still get the same issue, skillset and index, and connection to storage all fine.

Troubleshooting is not helping at all, as no meaningful error to start with.

Any ideas, absolutely driving me mad!

All suggestions and help, gratefully appreciated.

Dave