The meeting does not support dial in or call me to join. You cannot connect to the audio.

Replying because I FINALLY figured this out, and hopefully it will help someone else.

Before you join the room, hit the arrow and click PMI setting

and then, under the Audio section, make sure that "computer audio" is selected, it should have the blue ring next to computer audio as you see below. 

once selected, hit save, and then join the meeting. You may have to do this every time unfortunately, sometimes the setting will save permanently, but sometimes it won't. Hopefully zoom will fix this one day! 

Did not work for me.

Thanks a lot. It helped but I have selected Computer and telephone audio.

I checked my PMI setting as others have suggested and computer audio was not highlighted so I made sure to do that. It still did not work. For me, it ended up being a problem on the side of the person who scheduled the meeting. When they scheduled the meeting, under "Audio" they clicked "Computer Audio," since everyone joins on their computer. When they changed it to "Telephone and Computer Audio," those people who had been getting the "this meeting does not support dial in..." error message were now able to join the meeting with audio and mic working. Not sure if it was a mac issue or a Zoom issue or an internet issue, but all I know is now it works! I also went into Mac settings under Privacy and Security to make sure Zoom had permission to access my camera and mic (it did). Good luck! 

It is 2 years down the road but my husband has just been experiencing the same problem. None of the suggestions below work. I finally found it in the desktop version - Settings -> Audio . Scroll down to Ringtones and notifications and untick 'Automatically join audio by computer when joining' - when he opened the first meeting after I unticked the box, he was asked to select an audio option and he selected Computer Audio. It has been working (touch wood) ever since. It's weird as my own Zoom still has 'Automatically join audio by computer when joining' ticked and is working perfectly. Curiouser and curiouser! I hope this helps someone.