I have reached the threshold of $100/1000 but payment is not made.

The payout requests are formed on the 1st of each month.

First of all, make sure you added the payout method.
If you reached the threshold after the 1st of the month, your payment request will be formed on the 1st of next month.
Also, make sure that you meet the minimum threshold of your payout method. You can see them here. 

If you are sure that your payout was not sent by mistake, please contact your manager to resolve the issue.