Failed to authenticate on SMTP server, 0 possible authenticators

Your software
My PHP version is :7.4
My MySQL/MariaDB version is : MariaDB version

Installing Errors
I am : Installing
installing via (delete as applicable) : Web

These errors are showing in the installer : Failed to authenticate on SMTP server with username “service@accusoftservice.com” using 0 possible authenticators.

Your problem
My problem is :
I installed WP and SMTP Server on main domain (accusoftservice.com)
2. Then installed Mautic manually on Subdomain (mail.accusoftservice.com)

Completed:
Mautic Configuration Email Settings and
Test Connection = Success
But
Send Test Email = Error
(Failed to authenticate on SMTP server with username “service@accusoftservice.com” using 0 possible authenticators.)

Don’t feel like giving up