Thanks, Dave. I do have an OpenAI key -- in fact, two of them, one for each account. I think that one of these accounts does have some credit, but the second account has no credits (because OpenAI doesn't want people to use multiple accts to get around paying for more usage, which is reasonable). Anyway, executing
SystemCredentialKeys[All]
returns
{"wolframcloudconnect:www.wolframcloud.com&johnb@sfu.ca"}
The latter email address is also the user name of the "bad" account. I want to start over and use the "good" account, but I don't see how to do this. Executing
SystemCredential["OPENAI_API_KEY"] =.
does not work. (But maybe I didn't get your point -- does using any of the new LLM features in Mathematica require a paid subscription?)