A 401 User not found error from OpenRouter usually doesn’t mean the API key is wrong — it often happens when the server’s IP is blocked or flagged.

Since:

• The same key works on your local machine

• The same key fails even with a raw curl from your production server

• The env variable is correct

…the most likely cause is that OpenRouter has blocked or limited your Azure VM’s public IP (this is common with cloud provider IP ranges due to abuse protection).

What you should do:

1. Contact OpenRouter support and give them your server’s public IP.
   They can check and unblock it.

2. If you want to confirm it’s IP-related:
   Try calling the API from another server or via a different outbound IP.
   If it works there, the IP is 100% the issue.

There’s no problem with your API key or your code — it’s almost certainly an IP reputation block.