Invalid SIM number when trying to activate SIM throw API

I try to activating SIM cards throw Hologram API. But I can’t proceed the activation process, because of the error message “invalid SIM number”. In the past this worked, but for a while I had this problem. I am posting this here because I haven’t found any direct support contact. Any suggestions?

Please email support@hologram.io with the SIM number and they’ll be able to help you out.