@S1687
For MR6400 V4(the same as MR600 v1 or other models in beta firmware), the beta firmware provided the option to manually select the 3G/4G bands which the modem supported theoretically(all the listed bands), but not all the bands could be actually detected by the modem in the real network scenarios, which might be the first possibility.
(For the MR600 V2, it is a little different and all the listed bands could be in use.)
So in your case, it is quite like this one.
Then the second possibility, for the B41, for the EU version of MR6400, the bandwidth is between 2555-2655MHz and it has been reported that some SIM carriers use B41 from 2555-2655MHz to 2496-2690MHz. So we might need your help to check whether the Vodafone SIM is 2555-2655MHZ or 2555-2655 to 2496-2690MHz.