GDM3 login window not showing when monitor connected to graphics card port

Ubuntu 19.10 and 435.21 driver installed from Canonical repo. GTX 2080ti.

When monitor is connected to DP/HDMI ports on the graphics card and Prime select set to nvidia, GDM3 doesn’t show login window and no errors reported in any logs.
However, when the monitor is connected to DP/HDMI on the motherboard and Prime select set to intel, GDM3 works perfectly.

Tried to disable Wayland in gdm3.conf but that didn’t help.

Any ideas what might be happening?

Thanks!

Please run nvidia-bug-report.sh as root and attach the resulting .gz file to your post. Hovering the mouse over an existing post of yours will reveal a paperclip icon.
https://devtalk.nvidia.com/default/topic/1043347/announcements/attaching-files-to-forum-topics-posts/