In Microsoft Excel, spilled array formulas cannot spill into merged cells. Unmerge the cells, or move the formula to another range that does not interconnect with merged cells.

Once deleted, add the array formula again in the first cell and then copy it down to the required cells. Read: Excel ran out of resources while attempting to calculate formulas.

Microsoft Excel's dynamic array function XLOOKUP() might completely replace VLOOKUP() and HLOOKUP().