Please update me when you get a Vodafone SIM or 1nce SIM and flashed the nb-IoT FW to the Thingy:91.
I go the information that Vodafone is restructuring their IoT business and at the moment no new contracts are available. Alternatively Deutsche Telekom may offer IoT-SIM cards. I'll let you know.
By the way: I tried to use AT commands to connect directly to carriers. But it was not possible. Could you please check the default settings of the firmware. Perhaps there is an issue in the settings (e.g. APN).