carrier chiller 30ra/rh trouble shooting

Kindly someone help me urgently, i am attending above chiller, error message was 46 which is water flow switch failure.

1. I found there was no water circulation in the chiller. main water pipe was closed. I opened the main water tap.
2. I purged air in all the valves.
3. I switch on the unit, water pump was on but after few minutes alarm comes on (error message 46) & the unit shutting down.
4. I spoke with the technician in carrier chiller, they advised me to clean the strainer. i did that so, but still error comes on.

I checked outlet of the water flow switch, but there is a water when the pump is on.

kindly someone help me to trouble shoot this chiller.