I tried the same syntax which you shared and it works fine for me.
Select column1,date_column,coalesce(date_column,to_date('MMMM dd yyyy','January 01 0001')) from view_name
I recommend you to check the logs and execution trace to find out what is the error message that is thrown. It helps you to identify what is the problem. The logs can be found at <DENODO_HOME>/logs/vdp
If with that you continue having problems, if you have a valid support user, I recommend you to open a support ticket in the Denodo Support site (https://support.denodo.com), so the Support Team will help you to find the reason and solve it.
Hope this helps.