Failing to populate vector index using Bedrock

I am trying to follow the course from my own machine and I’d like to use Bedrock für the genai.vector.encode calls.
Doesn’t work for some reason. I validated that my credentials are OK in general, but the encode calls fail with {“message”:“The security token included in the request is invalid.”}
This is weird, as the Neo4j docs only list accessKeyId and secretAccessKey as required credential info. It does not allow me to send the session token.

Anyone tried that and succeeded?