Are you using VMware Tunnel and configured the settings in UEM?

https://docs.vmware.com/en/Unified-Access-Gateway/3.1/com.vmware.uag-31-deploy-config.doc/GUID-8B96F...

Here is a link to the techzone blog that walks you through the setup.

https://techzone.vmware.com/deploying-vmware-workspace-one-tunnel-workspace-one-operational-tutorial...

Let me know if this is on the right path and if you've setup everything as documented but still having issues.