As a workaround the C=DE in the GUI can be checked, then use the provision filter to achieve the required goal, so filter by required OU.
If above workaround provided does not work, then follow below steps and provide requested CMN DC Verbose log via a new service request:
1.- Set CMN DC Verbose log as per below KB article:
2.- Create a new O and OU below the C=DE, and see whether the OU is visible from the CMN DC wizard. Please use capital letters to set "O" and "OU" this time.
3.- Provide the corresponding CMN DC Verbose log for us to analyse.