iPhone 4s does bot activate

Problem started with iCloud becoming gray - I could not open it. Then I could not update software with my iMac as it required "find my phone " to be deactivated - iCloud in iPhone did not work thus I could not do it. Then I erased the phone via iMac and iCloud. It worked but now phone does not activate. It simple says that server could not be found even if sim & wifi works.