Symptom
The devices are detected by the UMS during a scan, but registration fails. UMS console shows an error message like "Unexpected end of input stream found at ...".
Possible Causes
The following causes have been reported with firewalls by SonicWall;
Large packets: See Thin Client Registration fails with Error Message "Unexpected end of input stream".
SonicWall DPI-SSL replaces the UMS certificate: If SonicWall DPI-SSL is enabled, it functions as intermediate CA and sends its own certificate to the devices instead of the original UMS certificate. As a consequence, the devices refuse to register because they would only accept the original UMS certificate.
Solution
In SonicWall, under DPI-SSL Status, add the IP address of the UMS server to the list of DPI-SSL exclusions.
Restart the VPN tunnel.