In order to see a plan in your Plans drop down list, you must have access and permission to view or edit that plan. You will automatically be able to see the plan if you have an assignment in the plan, either as the Assigned To user or as a Member of a plan card item, if you are an administrator of the plan, or if you are part of a team that's a member of the plan.
Otherwise, you will need to be granted access to the plan. Contact a Plan Administrator and ask them to provide you with access. To do this, they will need to:
1. Navigate to Plans > Select Plan.
2. Open a Plan Card and navigate to the Members and Admins area.
3. If you need to edit/create new content in the plan, ask your plan administrator to add you as an Admin. Otherwise, ask to be added as a Member; you will have view-only access.