Error on 2checkout gateway

Hi there,

I have sent this a week ago, but I am unable to fix it. I made sure that all the credentials are accurate.

(I have been approved for 2chekout and wanted to set it up. I have filled out the fields that needed to be filled and activated the gateway.
I am getting an error message:
(There was a problem connecting to 2CO. Please try again. REF:401)
How can I fix that?)