Problems with messages

Hi, from my new iPhone 12 sms cannot be sent, only iMessages. I have checked the settings and selected both options "iMessage" and "Send as sms".

May it depend from the fact that 2 iPhones are associated to my iCloud profile ? Because I can only send sms from first iPhone (1) and not the new one (2), although in the Messages menu in section "Send and receive" for phone 1, I associated the number of phone 1 and in the same section for phone 2, I associated the number of phone 2 ... Does anybody have an idea how the issue can be solved ? Thanks a lot !