Using VBA to enter a SumProduct formula into a cell

I need to use VBA to build a SumProduct formula and enter it into various cells in my worksheet. This is what I have done so far:

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When I try to run the procedure, I get Run-time error 1004 "Application-defined or object-defined error". The line starting with "ActiveCell" gets highlighted by the debugger.

The formula works fine when typed directly into the cell. So I have tried to use the macro recorder to record myself entering the formula, but then I get a message saying "Cannot be recorded."

Why is this error occuring and what would I need to do to fix it?