When I click start as host, Clients are on but they get message that I am in a meeting

I am a not tech-savvy senior who is relatively new to Zoom. I have hosted group meetings and not had any problems. 
Recently, I scheduled a number of individual meetings.  I sent a link to the client's email. When it was time to begin, I hit the start button next to the designated time from my meeting page.. When the meeting opens up,  I can see myself but the client is not there. They are getting a message that I am in a meeting that is in progress.

If I go to the email notification that the client has joined, I can get in through that link provided in that email and admit him into the same room. It's aggravating to me and annoying to the client also. 

What am I doing wrong?