Unable to connect to GMS with Google email application.

There was an updated pushed to update GMAIL application in November 2019. This corresponds a version 2019.10.20.x

After that you cannot connect to GMS with a security complain displayed on a phone.

There are more complaints over the recent application updates from November 2019 of the GMail application.

A trick to get it working again is to enable device security in GMS:

1. Login to webadmin console of GMS

2. Click on Config -> Devices. Here is the Device Security Policy option which needs to be activated. This is the minimum security settings that needs to be enabled.

3. Once you activate this option, save changes and restart GMS.

With this option GMAIL application / Android will ask you to enable policies:

You can review (click on Review Permission) what Device Administrator can do with your device:

Click on Activate at the bottom and the last step is to change screenlock settings.

Here you can choose PIN or password.

That works also with self-signed certificate used with GMS. However, since you might use iOS devices, we would recommend to replace self-signed certificates with any commercial ones.