Late reg is still supposed to be open, but I can't register to the tournament?

[User_41071]

There are 10 minutes left of late registration in an MTT qualifier, but the register button is greyed out, and I can't register?

[Uni-Rep]

Usually, this will be due to a cap on the number of players in the tournament:

Sometimes it can also be due to a design quirk when a player is eliminated very early in a tournament with only a few participants.
Below is an example from a qualifier. The player "bazookajoe" busted early in the tournament when they were just four players. If another player was allowed to join, 3rd would get a €2 ticket while 4th would get a small cash prize. As "bazookajoe" has busted early in 4th position, no further entries are allowed.