With the release of iPhone Xs, iPhone Xs Max and iPhone Xr Apple are changing the UDID format.
All versions VMware Workspace ONE UEM / AirWatch needs to be patched in order to support the new devices.
Patches are being released for the following versions of AirWatch / Workspace ONE UEM
If you are running a version of AirWatch outside of the above versions you will not be able to enrol new iOS devices.
VMware article below (that includes links for patch download):
Tunnel Proxy also needs to be updated:
Vmware support matrix is available in the following post: AirWatch End of support 9.2