I had exactly the same problem, each time I did anything in the I-Smart app I got the alert.
I tried locking and unlocking using the different methods, removing the obd dongle, resetting the infotainment system etc. to no avail.
So I took the step of powering down (locking the car) , disconnecting the 12v battery and reconnecting again. (I cleaned and greased the lead posts on the battery as they had no grease and were slightly corroded) Disaster after re-connecting and powering on again (sitting in the driers seat and depressing the brake for ready mode) one by one it told me that none of the assist features were working Collision assistance, power steering, LKA, FCA, RCA, cruise control etc.etc.
I reset the infotainment system - no difference, I locked the car and unlocked again, no difference, disconnected the battery and re connected and went through all the steps again with the same result. I drove the car a short distance but the steering felt weird, not self centring as you would expect.
So then I tried booking it in to the MG dealers (3 weeks wait and £180 diagnostic charge if not warranty related !!!!!!)
So finally I turned the car off using the menu option on the infotainment system and, with the car 'off' I pressed and held the home button to reset the infotainment system and lo, the system came back and worked perfectly once I had reset the windows, steering, and the MG assist defaults. It even fixed the original problem of the I-Smart app alerts.