The Player Log shows a bunch of these errors, hope they’re of some use @grant-rogers:
Fallback handler could not load library F:/Unity Projects/Project/Builds/Project_Data/Mono/tobii_gameintegration_x86.dll
Fallback handler could not load library F:/Unity Projects/Project/Builds/Project_Data/Mono/tobii_gameintegration_x86
Fallback handler could not load library F:/Unity Projects/Project/Builds/Project_Data/Mono/libtobii_gameintegration_x86.dll