I've been facing same issue with the RGB Plus 2.0 software. After using it for a while, display not connecting to RGB Plus, and I couldn't change the monitor screen. However, I could still adjust the fan lights (I'm using TH280 V2 ULTRA).
To resolve this, I uninstalled the RGB Plus software and reinstalled it again. Unfortunately, this fix is only temporary. After 2-3 days of use, the problem occurred again. I'm not sure whether the root of the problem lies in software or hardware lacks stability, and the user interface(UI) of software also seems incomplete and needs significant improvement. I'd suggest considering professional assistance, perhaps from a supplier, for better quality.
I think Thermaltake should be able to do better than this because the brand is positioned in the high-quality and high-price product category.