ISBLANK formula (as part of a much larger formula) not working
I am populating a column with the abbreviation for the month that corresponds to when a task was completed. There are many tasks on the sheet that have not yet been completed, so there is no date/month. My formula is returning "INVALID DATA TYPE" in the "Month Completed" for those cells in the row where the date is blank. I believe these instances for #INVALID DATA TYPE are keeping my Pivot from working. So, I am trying to use the ISBLANK formula to keep the cell in the month column blank when the Actual Completion Date is blank. I've tried a few different variations of the formula, but , so far, none of them have worked. My latest attempt is highlighted in the snapshot below.
Any ideas what I might be doing wrong?
Thanks in advance for the help!