It could be that some of the configs have changed their syntax or structure and as probably you used the update with kept settings - it mixed up and now your old configuration doesn't work.
Have you done a backup of your configuration on the earlier firmware? The only way to get it working right now I imagine would be through updating back to the earlier firmware and using that configuration backup to bring back the old configs.
Note that without a backup - rolling back to the earlier firmware will erase everything, will save nothing.
Regarding the warning that clients should get before updating - we always say that do not update if you're in production and don't update remotely if you know that something runs that you cannot set-up again on the go. But on the other side you're completely right, there shouldn't be such issues and update with kept settings should keep the device working as it worked before update.
In this case, 07.00 is a huge update to RUT9 devices, whole structure and workflow of the device is changed and that is totally normal to be breaking some features and services, so please next time if you see the update that has a long list of changes - you can try asking here if your specific functionality will stay working so I could consult with RnD before something like this happens.