People really should be using something like Sendgrid for smtp relay. Trying to tunnel through Gsuite or Office365 is difficult and constantly changing.
What I was suggesting is that you generate another email through the system. I.e. send an invoice to admin to see if it works now that you know the core connection works. But again, I'd put a marker in your PHP error_log file (a single line with the date/time) and then try to send the mail. If it fails, review the error_log AFTER your timestamp. If you need help, you can contact me through the 'get a quote' link in my signature. It won't be free, but it will be reasonable.
Make sure you turn OFF your secure app access in your Gsuite or Google account...that was the kicker for me. The settings above worked fine. Also had to make sure port 465 outgoing was open.