Additional meeting and call-related features and issues within Microsoft Teams for business
I finally found out my no sound issue is because I "joined meeting and not joined meeting."
Typically, when you join a meeting on a computer and then join the same meeting on another device, e.g. iPhone, Microsoft will ask whether you want to either "add this device to the meeting" or "transfer the meeting to this device". But when I do not have sound in Microsoft meeting on the first device, when I join the same meeting with the 2nd device, Microsoft will not ask me the question about transfer the meeting to the 2nd device. This tells me Microsoft Team does not know I'm already in the meeting on the first device. Hence, no sound for me on the first device. After realizing this issue, I signed out Microsoft Team on the first device. Completely closed Microsoft Team. Restart Microsoft Team and resign in. Join the meeting. Sound comes back.
At least this is a step better than reboot my computer (that was the only fix for no sound problem issue for me in the past).