Maxwell,
I have a LOT of experience with the absent button.
Example. you make a bet and hit "SIT OUT". Since you have started playing the hand it will not make you ABSENT until AFTER you have either hit or stand. Then it marks you as absent.
If you are absent and the initial bet has passed you and you it sit in you are still considered ABSENT until after the hand has played.
Why it does this I don't know. Your best bet is to hit the sit in button right BEFORE the dealer begins paying off to be considered present. Otherwise you may get locked out.
Also should you miss the timer you automatically become ABSENT - a good feature to keep the games going unlike slow poke Global when I usually fall asleep waiting for a match to conclude.
Hope that helps