Speakers "not plugged in" after upgrading video card - Windows 10

I'm going nuts with this, and have spent a long time googling the problem in various ways. Many have reported the problem over the years (a few in this sub), but I've tried the answers that have been suggested and haven't got anywhere.

I upgraded my video card, and ever since, neither the rear or front jacks for the on-board sound on my system work. I can only get sound out of my monitor speakers.

The 'speakers' device still appears under the 'Playback' tab in 'Sound' settings but it reports that nothing is plugged in.

Here's what I've tried:

• Checked speakers on another device. They, and the cable, are fine.
• Uninstall and reinstall sound card driver from mobo website (asrock)
• Uninstall and reinstall sound card driver from manufacturer website (realtek)
• Uninstall ALL audio devices from device manager (including hidden devices), reboot and reinstall
• Reinstall old video card
• Uncheck "disable front panel jack detection" on Realtek HD Audio Manager. Although this does allow me to use the 'test' function on the 'speakers' device, and the green bar lights up next to it when the sound should be played, there still is no sound
• Disconnect and reconnect front panel connectors on the motherboard
• The windows audio troubleshooter
• Disable, then re-enable on-board audio in BIOS.

I have tried plugging the speakers into both the rear and front jacks after doing all of these, but am still getting nothing.

I thought that perhaps I had damaged the rear jack by moving the tower around while I was installing it and the cable being pulled, but that wouldn't explain the front panel jack also not working, surely? I would really appreciate any help.

Edit:

• tried setting speakers as default in 'playback' tab in 'sound' settings. This option is not available while 'speakers' thinks nothing is plugged in. While unticking the front panel jack detection option allows this option to be selected, still no sound is heard.
• Made sure that the correct device is selected by clicking the speaker icon in the notification area.
• System restore to before the new video card was installed.

Edit edit:

Under 'audio inputs and outputs' in device manager, in the 'events' tab of the speaker properties, there is a line saying the device "could not be migrated," with the time stamp roughly matching when I first powered the system up after installing the new video card. There is a similar line in the events for the mic. I've searched this error and there isn't much out there. I have uninstalled everything in this whole device category, including hidden devices, restarted and reinstalled the audio driver, no change.