why doesn't my call waiting caller id work on my Iphone 4s anymore

Please define "no longer works".

Contact the carrier and ask them.

Those are carrier features.

there was an easy fix for my iphone 4 (and 4s) phone for his (Verizon carrier) Go to Settings, the RESET the NETWORK SETTINGS .

The phone will reset and the caller ID will show up with a Call Waiting when you are on the phone...