With this thoughtless deletion of customizing despite of having the values assigned in material master you actually created an inconsistency in your system. And if you change any other field in the material master you will not be able to save until you have removed this cycle count indicator as SAP will check the correctness of all fields when saving.
The selection for cycle count is a frequently asked question, you should search before posting a redundant question. Of course can a session not be created if nothing was selected.
But this has much different reasons than this inconsistency with the D in the cycle count indicator field.