@Uta - Hello! Yes, the activity is expected as a field is test is ongoing (yesterday and today). Additional logs from the 2 SIMs at of the day today via email would be again appreciated.

@Kolja-Vornholt The problem was as summarized:

I’ve set our modem to band 20-only. I want to use auto-attach (at+cops=0) but it did not find a network However, manual attach (with selecting Vodafone’s network) did work

Doing something else for about 30 minutes around the time @Kolja-Vornholt left the reply about searching the network.
Trying the search only gave me seemingly non-related info (“90104”),
But trying the auto-COPS suddenly did the trick and attached in no time.

So, it doesn’t really seem like a solution yet…

Carrier Aggregation, i.e. the linking of spectrum bands (Carriers) to a new virtual frequency band is a means to to offer high data rates for LTE-Advanced. However, NB-IoT is specifically designed for use cases with very low data rates and volumes, so there is no requirement for high bandwidth.