1. The HDMI 1.4B does not support Hdr splitter. Check if you had connected the Hdr splitter. 
2. The sync box currently supports HDMI version 1.4B, and the image quality supports Max Support 4Kx2K(3840x2160 4Hz/25Hz/30Hz) (4096x2160 24Hz),
3840x2160 50FPS/60FPS or 8K image quality is not supported temporarily.