Try deleting the standard master material and allow the script to rebuild it the next time you export. That might resolve this for both of you. If it doesn't, send in a ticket to support@quixel.se and our devs will look into this with you ASAP!,
I've also had this issue with 3D assets; asset imports but the material instance doesn't select the imported textures and the mesh doesn't select its instance of the material. I posted to the quixel discord tagging Adnan (the main dev behind the UE4 plugin) last night but haven't heard back yet. Pretty sure we could just…