No 144hz on 1440p resolution

Dec 31, 2018
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I recently bought AOC AG241QX monitor with RTX 2080 and I am unable to get 144hz refresh rate on 1440p resolution. I am using display port.
I tried changing display port from 1.1 to 1.2 but of no use.
Getting 120hz 1440p on dp 1.1 and 60hz option on dp 1.2.
The screen also blacks out as I restart my PC(not when switched off properly).
Please help me fix this issue.
I really need to play on 144hz refresh rate on 1440p resolution.
Thanks in advance.