Sm-dp address
It all of a sudden has no network coverage and say I need a sim code from my carrier
Question marked as
See this Apple article: If you see No Service or Searching on your iPhone or iPad
https://support.apple.com/en-us/HT201415
and say I need a sim code from my carrier
You need to contact your carrier.
See this Apple article: If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad