No longer able to access XG through Central

My clients XG was accessible via SC with no issues at all.

Recently when I click through to it the page reports its loading then I just have a white screen.

This is the same via partner access or via the client's credentials.
I tend to use in private sessions for access so web cache shouldn't be an issue.
I have updated and restarted it recently but the issue remains.

I can access the XG locally without an issue.