How put command in talkback queue whit visual basic | Other | Forum

Hi everyone.
I can't put talkback command with visual basic in the queue.
I use this:

https://api.thingspeak.com/talkbacks/TALKBACK_ID/commands.json?api_key=TALKBACK_API_KEY?command_string=OPENDOOR&position=5

in response I get the following:
{"status": "401", "error": {"error_code": "error_auth_required", "message": "Authorization Required", "details": "Please provide proper authentication details."}}

I can't understand what's wrong

Your suggestion is welcome