Does the HP have the right resolution if it is the only one hooked up?
I can tell you I have seen other complaints about resolutions other than the standard 1080, 1440, 4k etc over the past couple years in general and I have seen many complaints specifically with multi monitor setups with Navi in particular. I only wish I had ever seen a solution for you .
Also these forums are just USERS helping USERS. You might want to also ask AMD support: https://www.amd.com/en/support/contact-email-form
You can also talk to the support department of the company that made your GPU, they may be able to help.
If you didn't try setting up a custom resolution with CRU you might try that. It is a free utility from monitortests.com and see if that fairs any better.
https://www.monitortests.com/forum/Thread-Custom-Resolution-Utility-CRU