As to post #5 modify the formula to read:
Formula: copy to clipboard 
=IF(D4="","",(SUMPRODUCT(IFERROR(('MS-PS'!$M5:$AJ5)*($D4=GAPS!$A$3:$A$15)*(COLUMN(E$3)-$C4+1=GAPS!$B$3:$Y$15),0))))

Remember to simultaneously press the Ctrl, Shift and Enter keys after making the change and before copying to other cells.
As to post #6 when I change the date in cell E3 on the MS-Cashflow sheet from 8/1/2018 to 9/1/2018 (I am working with the file attached to post #2) it causes cells C4:C8 to display #N/A and E4:AU8 to display blanks, so I imagine that I am missing something else that needs to be done when that date is changed. Please either explain all of the changes made, or upload another file that demonstrates the issue.
Let us know if you have any questions.