Until you find a permanent solution, see if this workaround helps when you encounter the problem:
When a program starts with no audio, try pressing the rewind button. I find this almost always restores the audio. Once in a long while I may need to do this more than once.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X