Unable to set the FormulaArray Property of the Range Class - Error 1004

I'm new to VBA, but have been using Excel for many years. I'm sure this is a simple problem that others have asked about, but I can't seem to find a solution.

I'm just trying to fill the cell that I have clicked (which will always be the "L" column) with an array formula. I have to do this repeatedly with different filters on my data but not for the whole column. I'm getting this error: "Run-time Error '1004', Unable to set the FormulaArray property of the Range Class."

I have made sure that my formula is not longer than 255 characters, and I'm pretty sure that the arrays are the same size with no replacement.

Any thoughts? Thanks in advance.