Mini Cooper Electric immobilizer problem

Sounds like a classic immobilizer fault. Does it crank at all, or just nothing? When you say 'error stored in the error memory,' can you be more specific about the code? Intermittent starting is often a sign of a key transponder issue. Have you tried your spare key, to rule that out?

It cranks, but doesn't catch. The exact error code I noted was related to key authentication. I haven't tried the spare key yet, that's a good suggestion. If the spare key works, does that confirm the original key's transponder is faulty?

Yes, if the spare key resolves the issue, then your first key's transponder is more than likely the culprit. Given the stored error code and the symptoms you describe, the car electronics are definitely suspect. A workshop with the proper key programming equipment should be able to resolve it fairly easily.

Thank you for your input. It turned out the key programming was indeed the issue. A quick visit to the workshop and 45€ later, the Mini Cooper is back on the road.