I open it from the ribbon menu.
I wonder if it is because of how I have the variables. The variables have a list that includes a SQL statement that takes about 10 seconds to return. The status bar says "Initializing...", it flashes after the 10 seconds and then nothing. If I click on the pl/sql Developer icon on the start bar after the flash, then the "Variables" window shows up.
Here is how I have the variables:
AND h.user_concurrent_program_name = '&'
AND nvl(h.actual_start_date, SYSDATE) >= to_date('&', 'dd-mon-yyyy')
AND nvl(h.actual_start_date, SYSDATE)