GRE Hangs at loading when trying to request a new restore


We currently have 2 environments at 2 different locations in an active / active configuration. Both site are identical in setup.

HP B6200 StoreOnce VTL

2 x Media server per site
DP A.09.07 build 109
Vsphere 6.0.0 build 3271482

GRE agent version and plugin version are not being displayed from the about section

For around 1 month now we have lost the ability at both sites to restore through the GRE plugin. As far as we can tell, nothing has changed from an infrastrutcure perspective and no updates applied.
When click on the plugin each screen (GRE Settings, GRE Requests etc) the screen hangs and just says loading and goes no further.

Our Network team has checked the firewalls and all ports are open.

Has anyone experienced a similar issue?