First thing is to just restart the laptop and the RokluTV. (Settings/System/Power/System Restart).
Then when you go to cast again, look on the laptop/PC under the Sound options and see if you have to switch output to the casting recipient. (ie. maybe Settings/Sound or the Taskbar and see if you have to disable laptop speakers, select audio source, or turn up volume slider to desired output). Some of these options may be under "More Volume Options".
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102