I very much doubt if a Windows 8.1 driver is available. Review this post. It seems that this particular tuner was going obsolete. If you google the tuner, you should find a Windows 7 driver here. That might not even solve your problem.
I had this same tuner card in a VISTA PC and I did manage to get it working with Windows 7.
If you search the forum, you will find that some were plagued with problems using the VIxs tuners. The model might be different but the issues could be similar.
HP ENVY 6055, HP Deskjet 1112 HP Envy 17", i7-8550u,16GB, 512GB NVMe, 4K screen, Windows 10 x64 Custom PC - Z390, i7-9700K, 32GB, dual 512 GB NVMe, dual 512 SSDs, 4K screen, OC'd to 5 Ghz, NVIDIA 2080TI 11GB
I have the same issue. The Windows 7 driver will not install under Windows 8.1. I downloaded it, and ran it, and it gives an error message stating that my sysem did not meet the minimum requirements. Everything is in excess of their minimum requirements except I am running Windows 8.1 and not Windows 7.
Typical HP. High priced machine that they will not support beyond the original operating system. I have no choice but to pull the ViXS card and trash it. Let me know if you find a solution.