on screen navigation bar not working

[0101chaitanya]

guys my lenovo p2 with stock rom was working fine untill yesterday night . i woke up today morning to find that the on screen navgation bar is not working ( not responding to touch ) i tried disabling it the area is working in that case all bottom apps after disabling so i flashed latest 15.1 lineage os according to instructions but the problem is still present please help im finding it difficult to use tq