Upgrade error

[MyriamM17]

On the 26th of July I have upgraded my account to be able to host a zoom call with more than 300 pax, on the 27th I had my masterclass where not more than 100 pax were able to join and many more sent us an email stating that Zoom isn't letting them in because of the call link was closed / full. 

This error actually made me lose customers. Please I need an explanation and a solution. 

Thank you!

[Ray_Harwood]

Welcome to the Zoom Community, @MyriamM17.

After you (or your account owner or admin) purchases an add-on license, it must be assigned to the designated user.  See this Zoom Support article to information:

https://support.zoom.us/hc/en-us/articles/115004976063-Assigning-Zoom-licenses 

Also note that the Large Meeting add-ons are for 500 or 1,000 attendees.  The only way to get a 300-attendee limit is to be on a Business Account; Pro account default attendee limits are set to 100 attendees.