I have the exact same issue. Cannot update to 11.3-U1. Get erroe "Unable to connect to url
https://update-master.ixsystems.com/FreeNAS/FreeNAS-11.3-STABLE/LATEST: Automatic update check failed. Please check system network settings"
System is able to update the jails, DNS resolves correctly. Tried link from computer and the site is not available
The download page only has the .iso and no update packages either so cannot do a manual update. Unless the manual process now uses the full .iso?