Items (e.g. polls, quizzes) that were created from accounts that exceeded the monthly plan limit are signaled as disabled. To enable them again this month, the account needs to be upgraded.
For example, if the account that created the item is on the free plan, and the account items got more than 250 views this month, then all your items will be disabled for the rest of the month. The items will automatically re-open next month until the 250 views limit is reached again.
For details on plans and views/month limitations, refer to the pricing page