External Monitor Stopped Working on HP Spectre 360

[sk_moy]

Yesterday (and for the previous 10 months) my laptop was connected to an external monitor. This morning, it seems that it can no longer see the external monitor. I have tried connecting another laptop to the monitor and that worked. I have also tried connecting the laptop to a different monitor and that didn't work so I think the issue is with the laptop.

I've tried updating the graphics card driver and manually re-installing the drivers for the monitor. 

Any suggestions on other settings or elements to check would be appreciated?

I guess at worst it could be an issue with the graphics card  but there is no problem with the laptop display so is it possible that the graphics card could have an issue without impacting the laptop display (i.e., and issue that only stops it seeing external monitors)?

Final question, if it is the laptop card, can the graphics card be replaced in a HP Spectre?

[sk_moy]

After some further testing, if I connect my monitor using a USB 3 adapter it works so it looks like the issue is with the USB C ports. So far the laptop is charging but anything else seems to have issues when connecting via USB C ( also tested a USB C Ethernet adapter). 

Why would the USB C ports work yesterday and not today?

[sk_moy · Accepted solution]

OK, finally decided to ignore the HP diagnostics and update tools, and manually reinstall the latest BIOS and Intel Thunderbolt Firmware Pack. This fixed the issue.