Google Calendar Feeds in GroupWise calendar now fail

GroupWise Client 8.0.3 HP3 (build 105538) Windows XP SP3

For a long time I had my Google Mail Calendar shown in my GroupWise Client as a separate entry using the Internet Calendar function. The location something like this (with the sensitive parts altered):

For a few months now I've noticed it no longer works. Nothing in the client has changed same version as before. I can browse to the URL from my PC and appear to get a valid ics file. I've tried both https and http in case GW8 doesn't support some of the later SSL/TLS protocols, both work via a browser, neither in GroupWise.

Anyone use this and still have it working?