Hello @Jeluani12,
The error message means the private key you entered is not in the correct format.
You need to use the exact value from the private_key field in the service account JSON file, including the BEGIN/END PRIVATE KEY headers and the \n characters. Don’t rewrite or remove line breaks.
Even if the test keeps spinning, try using the credential directly in a Gmail node; if it still fails, it’s almost certainly a key formatting issue.
Thank you for taking the time to answer my question. I’m still very new to this, so I’m watching more videos before continuing work on my first N8N automation.
Ehy @Jeluani12,
If you wanna some help we are here to answer your questions 
If you wanna some hints for building workflows you can write into Help me Build my Workflow channel.