My Zoom account

Hello

I have been using Zoom for a few months. My students used to get on using the same session number and passcode. However, as of last week they can no longer use the session number and the passcode. They get a message that the host is holding a meeting and they cannot  get on. This is not true. Is it possible that my zoom account has been hacked and that's why students can no longer get onto my session? Now, I have to send a session number and a passcode before each session which is time consuming. What do I do to get my session number and passcode back? I have written to Zoom's support centre but nobody has replied. 

Thank you for your time and help.

Brigite Assis