Dear @Ramanan_Balakrishnan, you say that no one received an email invitation. However, I see that you have some members were listed in the invitation box of the meeting (required attendees) and they are indicated as having accepted the meeting invitation. That is how it works.
Unfortunately, the members do not get an automatic notification and at this stage there is no way to invite a group as a whole. You will have to add each individual to the required attendees box - then they will receive an invitation.
Either you have to inform your 250 professors in another way of the meeting, or you need to add 250 members to the required attendees box. That is A LOT of adding!