#VALUE! Error

I want to simply add 5 cells together in cell M25.  I have never gotten an error on a formula that is so simple!  I am getting error message #VALUE! when I try to enter either of the following formulas into cell M25: 

=SUM(C26+E26+G26+I26+K26)

=C26+E26+G26+I26+K26

I have the same type of formula in the cell M26 below and it is working.  I tried to fill up.  

=SUM(C27+E27+G27+I27+K27)

Tried: 

I have copied the formula in cell M26 and tried to paste it into the cell M25.

I clicked on the cell and selected delete.

I have right clicked and cleared contents.

I have tried to Find/Replace looking for hidden spaces and text in the cell.

I have verified that the cells are all formatted to number. 

Any help would be great,