Custom columns that don't work on the web

I have a formula in my model that the website version doesn't seem to like.

In my query, I have a custom column that counts the number of days between 2 dates

Both the CreateDate and PMStartDate are date only fields format as MM/DD/YYYY with no time.

It works really well on Power BI Desktop.

When I upload it to the web, I get an error on any visualization that has the custom column.

Is there some reason why the website doesn't like the formula?

Is there a better formula to use to calculate the number of days between 2 dates?

Thanks