Microphone muted on desktop when the meeting starts

[Willians]

I've been using ZOOM in my classes for the past 3 years or more and I had never had any situation like the one I've been facing. Every time I start my classes I have to UNMUTE my microphone and it had never been like that before. I don't want to start the meetings muted. I want my microphone to be ON every time. Does anybody know where or how I can fix this? I've already spent hours changing settings here and there but nothings seems to work.