OLD RULE

If you switch teams in the middle of an event, your points will stay with your previous team. Any new points you earn will only count towards your new team if said team are in the same league as your previous team.  At the end of the event, you will be able to receive the rewards earned based on your new team's ranking.

Other reasons for not being able to score is when someone on the team was able to perform a team quest progression. Once they progress, they are registered as part of the 50 contributors. For more information of who are those contributors, they are the ones placed between number 1 - 50 on the team contribution page under Event Page > Prizes and Ranks > Teammate Contribution. Players with the N/A and at the same time, a number is showing, it means that they were once part of the team, contributed and left the team or kicked out for unknown reasons. Those with no number are players that was not able to contribute or progress through their team quest before the others or a recently recruited member.

NEW RULE

If you switch teams in the middle of an event, your points will stay with your previous team. Any new points you earn will only count towards your "Personal Points" during Breeding and Fortification Event. If you join back to your original team, your contribution there will start counting again. However, it will not count all the points you earned outside so even if you see that you have 400,000 points there, if you quit while you were at 200,000, then only 200,000 will count and it will only start increasing once you join back even though visually, it is seen as 400,000 points.

Eligibility

A few hours before the start of the event (No exact time), the system will start registering all team members as part of the team for the event. This is done to prevent old members from being ineligible because of the old rules where you will be registered only if you started gaining points or doing the team quest.

Under the old rules, if 5 members that already gained points was kicked and then 5 new members joined to replace them started gaining points before any other members, then 5 random old members that is still part of the team will become ineligible. This is why early registration of team members was implemented to make sure that no old members are prevented from participating in the event.

A team can only have 50 eligible members. Once a team has 50 eligible members, any new player joining will be marked as "Ineligible". A specific reason will be given if you tap the "Ineligible" button. Here are the possible reasons that you can see:

"Ineligible to join event for team < TEAM NAME >

This player is ineligible to participate in the current event for this team because they left the team < TEAM NAME >
This reason is given if the player is already registered to a certain team. This player will become eligible again once he joins back on that team
 
"Ineligible to join event for team < TEAM NAME >

This player is ineligible to participate in the current event for this team because the maximum of 50 players have already contributed points or participated in Team Quest in the event for this team.
This reason is given if the current team this player joined has 50 eligible members already. This player will become eligible if it joins another team with less than 50 eligible members.
 
If you leave your team after the event starts and before you received your team prizes, then you will not receive your team prizes for the team you earned points for. 
 
Atlas

For Atlas related events, you can still gain points, but will not be able to contribute for your team if you join in the middle of the event. Even if you joined back to your original team, future contribution is turned off until the next event goes live