Zoom chat direct messaging disabled

In my most recent Zoom meeting (which i hosted), the participants were not able to send direct messages to each other - only messages to the whole group were allowed. There was a message saying something about "because you have a large number of participants of this meeting, direct messaging is disabled" or something to that effect. There were less than 20 people in the meeting, but around 70 invited. This has never happened before even though this is a recurring meeting with the same number of invitees each time. 

At the beginning of next month we will be hosting a conference with 200+ people in a meeting, and we would like to keep it as a meeting, and not a webinar, precisely because we want participants to be able to interact with each other. Is there a setting which will prevent Zoom from disabling the direct messaging feature for large meetings?

Thanks!