On-board sound card issue when running pro tools

[Tsen Ru]

BACKGROUND: I am running both an external audio interface (exclusively for pro tools), and an onboard sound card (for all other apps).
This setup has been successful in allowing me to simultaneously use PT through my studio monitors, and youtube, etc though my laptop speakers.
ASIO4All is installed to facilitate this setup.

PROBLEM STATEMENT: This setup was working fine until yesterday. PT still works fine, but when I have PT open i can no longer play non-PT sounds through the on-board laptop speaker.

CURRENT SETUP, AND OTHER STEPS ALREADY TAKEN:
1. ASIO4All is installed and successfully recognising the two sound cards.
2. PT Audio engine is set to ASIO4all, and track sample rate is set to 48khz for all PT projects.
3. External Audio interface sample rate is set to 48khz in windows sound settings.
4. ASIO control panel is set to 48khz.
5. On-board sound card sample rate is set to 44.1khz in windows.
6. Both audio playback devices are enabled in window sound settings, with the on-board sound card set to the default playback device. Within windows device properties, the "test" for each device works fine.
7. In window sound settings, all Recording devices are set to enabled, with "Stereo Mix" as the default.
8. All latest drivers are installed
9. I have already tried deleting the AVID appdata files

SPECS:
- Laptop = ASUS ROG with Intel i7-7700 CPU
- DAW = Pro Tools 12.8.1
- OS = Windows 10
- ASIO4all
- Audio Interface = Focusrite Scarlet 2i4 (1st gen)
- Internal sound card = Realtek HD Audio


I do not remember making any significant changes to my setup, although i do move the laptop to various locations that sometimes I need to tweak the sound card settings for, so it is possible i changed something...

I have searched various forums for something that may assist in remediating this issue, however I am yet to find a solution - Any help would be greatly appreciated.