RV50X not connecting to provider Telia in Sweden

we have purchased a SW 1102555 RV50X Sierra router (NA version). This version is supposed to be suitable for LTE bands in Europe. Recently installed with Telia prepaid SIM in Sweden and could not get it to establish network connection. Left it for 1 day and it did finally connect at 3G but then dropped out again soon after. The signal strength is very good.
Looking at the Telia frequency bands: they operate 4G LTE on 800, 900, 1800 and 2600 MHz i.e. B20, B8, B3, B7. This lines up with what the RV50X can do (according to the data sheet). The router is about 1 year old and I haven’t updated the firmware.
Any suggestion on what to do to make this work.
P.S I have used the RV50X Asia Pacific versions many times so know how to enter the APN and other data.