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I am not successful in connecting 2 LTE CAT M1/NB-IoT Shield to a working operator using a Hologram SIM in Berlin Germany

Verified the SIM is active, I sent and received SMS using the SIM in a mobile device

The message in Arduino Serial is
"Did not find an operator. Double Check SIM and antenna, reset and try again or try another network"

have tried reset
Hello, and thanks for your post!

It sounds like you might be in a poor reception area where the shield has difficulty getting a cell signal. You might try a different location or going outside to see if you get a signal there. The antenna on the shield is OK but not great at getting a signal in a weak signal area.

Another option would be to try an external antenna.