BMW engine overheat message, no CEL error code

This is regarding 2005 745LI, I have recently changed coolant Thermostat,
Upper and Lower Coolant sensor and Radiator fan. I keep on getting Engine
overheated at 107C. The Water pump is working fine as I can c a steady
stream of coolant in coolant reservoir. The coolant is between Min and Max
range (no coolant leak).

Upper radiator hose is HOT and lower radiator hose is warm to touch.

I am able to drive for 30 mins continuously and the message keeps on
popping and disappears and this cycle continues.

Also the radiator fan does not come on when the overheating message pops
up. Only when I start  the AC, the fan starts.

Any help is demystifying this issue is much appreciated.

Thank you.