If "Accept" button is greyed out, it means you are already part of another team and you are the only manager in that team. You have been given three options saying:
This invitation can't be accepted unless:
1) Your role in the invitation from the new team is changed to collaborator
2) You add a new manager to your existing team
3) You delete the assets in your existing team
You have to follow any of the steps above and reload the page, you will see the "Accept" enabled
This invitation can't be accepted unless:
1) Your role in the invitation from the new team is changed to collaborator
2) You add a new manager to your existing team
3) You delete the assets in your existing team
You have to follow any of the steps above and reload the page, you will see the "Accept" enabled