Your best bet would be to delete the old Device Handler and Smartapp. You can then either add the repo from tobycth3 (https://github.com/tobycth3/SimpliSafe) for each item or you can manually create a new Device Handler and Smartapp. The code for each is below:
Device Handler: https://github.com/tobycth3/SimpliSafe/blob/master/devicetypes/tobycth3/simplisafe.src/simplisafe.groovy
SmartApp: https://github.com/tobycth3/SimpliSafe/blob/master/smartapps/tobycth3/simplisafe-monitor.src/simplisafe-monitor.groovy
After you add the Device Handler and publish it. Goto “My Devices” and add a new SimpliSafe device from that handler. Once created you will have to edit the device, and under preferences enter your Username, Password, and the type of system (ss2 or ss3).
That should get you back up and going.