Your HP Monitor seems to support Freesync.
Go into the Monitor's Menu Settings and make sure you have Freesync enabled. There are about, I believe, 3 different Freesync modes to enable.
Here is AMD's Freesync FAQ concerning the above modes and how to enable it: https://www.amd.com/en/technologies/free-sync-faq
According to the AMD Freesync Monitor list your monitor only support Freesync mode only and doesn't support HDR. So make sure you have HDR disabled in Windows Settings.
Doesn't support Freesync Premium nor Pro modes.
Also go into AMD Settings and make sure you have Freesync enabled there also.
So make sure you have both the Monitor and AMD Settings with Freesync enabled.
EDIT: You never mentioned what AMD GPU card you have installed. Maybe it is an old one that doesn't support Freesync.