This is quite odd, but I’ve heard of this situation before. It most likely a combination of things.
I would recommend that you reach out to our customer service for specific technical support. They will probably need to request your logs to see what happened behind the scenes for this to occur. They can be reached via email at [email protected] or, alternatively, you can submit a support request/support ticket directly on our website:
Thank you so much for your help. I submitted a ticket and your colleague told me to ask my service provider. This was the right way: It was no “Mudita Problem”. My service provider fixed it and now i can send SMS.