Hi Phil & Torsten,
My organisation has the same issue. We tried to catch the URL called by S123 when login-in/retrieving the list of available surveys, but we were not successful.
Would you have any hint/pointers for us? The idea would be to adjust proxy setting to let those URLs through (I think - I am no IT specialist, so this is my basic understanding of it!)
Note that we successfully use Collector on the same enterprise network, because the URLs are exposed.
Many thanks!
Hélène.