I am running Cyanogenmod on my Galaxy S2 for about a year.
A few months ago I bought a new phone and game my Galaxy S2 to my mom to use as a second phone. I did a Factory Reset before that. Everything was working fine, including root.
Recently I took the phone back and did a Factory Reset again, but now I lost root access. It is set to "Apps and ADB" in developer options btw.
I tried reinstalling Cyanogenmod, no luck. Tried flashing recovery (I am using clockworkmod and it worked file all the time), no luck.