UHD 4K not working on XG1v4 Cable box for Netflix and Amazon Prime

I was able to watch Netflix and Amazon Prime in UHD HDR on the 4K X1 DVR XG1v4 earlier last year on my Samsung 4k TV.  I have not been able to watch these this year via the same X1 DVR.  But via the same X1 DVR I can watch Youtube and other X1 native shows in 4K. The X1 video resolution is set for 2160p30 4k UHD.  I have checked the Netflix subscription that is still set for the premium plan.  I deregistered and re-registered both Netflix and Amazon Prime but that did not help.  I rebooted the DVR, reseated the cables, but no luck.  If I directly watch Netflix or Amazon Prime via the Samsung app, the 4k programs appear in 4K UHD HDR.  I called Xfinity support but their Level support was unable to help.  I will try the Xfinity level 2 support. If anyone has come across such an issue and found a resolution, please do help.  Thank you!