Issue with Bicep usuage(subscription)

Good day,
My name is Rodney Effah and i need your help with my account as it keeps saying 'multiple accounts with the same username'. That's the error that pops out whenever i use this command: az deployment group create --resource-group testgroup --template-file main.bicep.

I am trying to use the sand-box on microsoft learn. Can you please help me with this.
Thank you.