just for clarification: That means you did not use SNAP before (and therefore cannot tell if it has worked correctly some days ago, or with an earlier version, for example)?
I have used SNAP many times before (V5) but not recently. It may be caused by our firewall, but I do not know. If you want I can send you the full error message.
Currently, the used location for orbits for S1 is https://step.esa.int/auxdata/orbits/Sentinel-1/
so my guessing is that some old setting/preference from SNAP 5 (that you previously used) was not deleted.
Try to uninstall SNAP by choosing to delete all previous SNAP data/settings and re-install it.
You’re right.
For S1, I see that the download from QC (using REST API) is tried before the download from STEP auxdata (location indicated previously by me).
I tried a request to QC and it works, so I think the issue is probably on your side: