Hello
@RodMuir,
To help you better we'll need more information:
- What is the make/model of the Thunderbolt monitor?
- You're using an Nvidia GPU, so are you running Sierra or High Sierra?
- The Quadro P400 is a Pascal-based card so it should also run under Mojave and Catalina, but I have no experience with Nvidia GPUs on current versions of macOS.
- Have you tried switching to Platform ID 0x3E9B0007?
- The Thunderbolt monitor can only be connected to Thunderbolt Port 1, the port closest to HDMI.
Hello Casey
In answer to yours questions.
Apple Thunderbolt Display, 27” (2560x1440). From the bottom of the stand, Model Number A1407. Assembled in China.
I’ve got Catalina 10.15.4 installed.
Don't know how to switch to Platform ID 0x3E9B00007 or what I would need to do that?
The Thunderbolt is connected to Port1 closest to the HDMI.
Also there is some information on 1616 #16,168 that specified how to change the ThunderboltDROM but I can’t work out what or how to open anything here. Anyway not sure if that matters?