tried all the above,none worked,decided to take screen off, reassemble without screen,after this i connected screen externally,made a phone call and put finger over pair of sensors,still not working so the next step is to replace sensor cable.
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UPDATE,
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replaced flex cable, uv filter, foam surround used 2 one on top of other,genuine used but in excellent condition screen,
tried all the above,none worked,decided to take screen off, reassemble without screen,after this i connected screen externally,made a phone call and put finger over pair of sensors,still not working so the next step is to replace sensor cable.