Google recently transitioned to using an authentication scheme called OAUTH 2.0 for Gmail. The Windows library that is used in InduSoft Web Studio (Collaboration Data Objects) does not support OAUTH 2.0 so the SMTP connection gets dropped after the InduSoft Web Studio credentials are sent.
Gmail implemented OAUTH 2.0 earlier this summer, but gives you a way to opt out. Note that after this change is made, the required access does not seem to take effect immediately. However, waiting several hours after the change is made seems to allow the email to work again.
After you make the changes to Gmail, then you need to open your InduSoft Web Studio Project >> Email settings from the InduSoft Web Studio ribbon menu and configure it similarly to the following image: