What does the logging in your console tell you? Can you share the stack trace?
Did you try the automatic config as well?
Please check below points
1. Ensure that the userLib folder contains the required Jars (no conflicting jars). Most likely you are still using jars from previous email modules. Prerequisites can be found at https://docs.mendix.com/appstore/connectors/email-connector/#12-prerequisites.
2. If you provided the gmail account details (email/password) on the connect to email account screen, it should have auto-detected the gmail server settings, which does not appear to be the case.
3. Use the App password for Gmail https://support.google.com/mail/answer/185833? hl=en
I found the issue that was causing my application’s Email Connector setup not to work, maybe this will work for you.
It was a JAR file issue.
The file javax.mail-1.6.0.jar that existed in the userlib was causing problems.
That said the JAR file causing this for you may not be the javax.mail-1.6.0.jar file as well. In that case I recommend that a comparison of a new app where the Email Connector module has been imported against the existing application.