All my files appear Offline after system reinstall

I've done a motherboard replacement and reinstalled Windows. System works well with everything but Resolve Studio shows all my files and projects offline both in the timeline and in the media page.
If I try to play a clip I can hear the sound but no video. Looks like this is on all my projects whether source files are 422 or 420

What I have tried:
- Reinstall HEVC extension - (the files play well in both VLC and Media Player)
- Relink files in the media page
- Move the files from a project to a folder on the C: drive and try to create a new project with them
- Reinstall Resolve
- Delete render cache
- Update GPU drivers

I use Resolve Studio 19.1.4 / Windows 11
System is AMD 5900x / Gigabyte X570 Elite / rx6700xt / 32gb ram
All files are on internal HDDs or NVME / SATA SSD for cache / All drive letters are identical as previously

Hope someone can help

I managed to fix this by disabling Decode H264/H265 using hardware acceleration in the Preference>Decode Options
This is strange as this RX6700xt card was used before the mothboard swap and has 10bit 420 hardware decode support.

In the lower left corner of the GUI, confirm you're using Studio.

Yes, I am using Studio

Update:
After trying previous version of the GPU driver (didn't work) and the Resolve 20beta (same problem) I'm back on 19 and the only way to not have Media Offline is to enable Decode H264/H265 using hardware acceleration but disable the AMD option just under.
This way, it looks like the GPU still does the decode but not using its media engine?