protontricks-launch fails but executing from Dolphin works

[schradert]

When I open my game launcher in Dolphin and hit execute, the protontricks GUI opens and I can select the Wine prefix for the non-Steam game this launcher is for, and the game opens without issue.

I expected the non-interactive version of this to be protontricks-launch --appid <appid> <exe>, but when I run that, I get a somewhat classic alert: This application failed to start because it could not find or load the Qt platform plugin "windows". This is the same error I get when running it through steam.

Any ideas what could be the cause of the difference, or how to investigate what that is, or even what might be the right fix?

I'm not sure if this is an issue with how I'm using protontricks either, but I thought I would start here in case anyone has seen this behavior before.