Thanks for reaching out.
The logs indicate a problem logging in. Did you click the Test Connection button in the RBE settings screen?
You may have to enable Less Secure Apps in Google: https://support.google.com/accounts/answer/6010255?hl=en
Note that as Google is disabling Less Secure Apps in 2021, the upcoming version 3 of RBE will provide a more secure way of connecting to Gmail.
Let me know how it goes.