Not able to control Simplisafe from phone

I have replaced my modem and router, I have changed my internet service from Xfinity to AT&T.  I am no longer able to access or change my system status with my Android phone. The phone is connected to both wifi when at home and data when away.  I have deleted the Simplisafe app and reinstalled it, still will not allow me to turn the system from off ,home or away on my phone.  I do not believe the system will contact the monitoring system if there is a entry violation. When looking at my camera I get the message that the system is off line.  Please help me get this problem corrected.