No TV sound all of a sudden

Hi there
I had to mess with my computer second screen settings and now I get no sound on my Samsung smart TV when using Pluggable. The playback settings box says USB3-HDMI-DVI is not plugged in, although it is.
I try to make it a default but it is greyed out.
Can you help please. It happened once before but I cannot remember the resolution.

Andrew contacted us via to let us know that a system reboot resolved the issue.