The Show only distinct values option for SAS Stored Process prompts might not work if all of the following conditions are true:
You encounter this issue if the above conditions are true and you complete steps similar to the following:

There are multiple workarounds for this issue:
Workaround 1:
Enter a value into first prompt and move to second prompt by pressing Enter or the Tab key.
Workaround 2:
Click the down arrow to specify a value in the first prompt.
Workaround 3:
Right after you open the stored process, select Reset group of defaults.