Has you changed your SIM card when you go to other countries?
MR200 can work only when the SIM card's frequency is supported by it.

no i have not,the card is compatible with either 3g, lte, edge, gprs with Fritz box 6820 it works automatically. Does the MR200 not automatically Switch between the Network frequencies? Can that be the Problem?

Same problem. Worked fine in Norway with a Norwegian SIM card from Telenor. Could not connect in Germany With the same SIMcard.

Solution was to manually configure a new profile under Advanced, Internet. PDP type = IPv4&IPv6, APN Type=Static, APN = Telenor, Username & Password empty, Ath. Type = NONE. Then it worked fine. I received the values to enter from Telenor helpdesk; you probably have to call your own SIM card operator.

I think the problem is that the profile is automatically loaded from the network. In my case the aoutloaded profile was from Vodaphone, which does not work since I have a Telenor subscription.