has that sim ever been used on a different cell number? most sim cards can only be programmed to one cell number they cannot be swapped. and after 90 days of being inactive most sim cards expire as a security feature.
" Invalid sim " indicates that your phone is locked with your carrier . Whats your mobile manufacturer and model ? To unlock your phone from carrier lock, use unlock code to unlock it . You can get it from any of the online vendors like http://www.unlock-zone.com/supported-... to unlock it .