We try to send out most invitations at a time that will be convenient for most testers. However, to avoid unnecessary rejections of testers, our system automatically only invites a few people at intervals until all available spaces have been filled by testers. That means we can’t always influence when invitations are sent.
It works like this for example:
We need 30 testers, so the system invites 50. Out of those, 15 accept the invitation within the first two hours, and 15 are still missing. Then after a while, the system invites another 30 people, which leads to another 10 people signing up. However, 5 are still missing, so another group of invitations is sent. This continues until we have enough testers or the sign up phase has ended. We think this system is better than inviting all testers that fit the criteria right in the beginning, because that would mean disappointing a lot more people.
So if you get invitations shortly before the test is full, this likely means that there was only one spot left and someone else took it before you.