I am finding this very frustrating, I open Excel, New workbook, no protection, no sharing.
I start making my sheet with every second row elongated vertically to the height of two cells, no problem. Then Horizontally I want to merge certain cells into one bigger one. The first row I merge 4 cells into one big one, when I try to do the same thing on another row nothing happens.
I have tried "Merge & Centre" "Merge Across" & just "Merge Cells" but after the first row nothing happens. I need to print the grid lines and the boxes of differing sizes.
I am only a basic user of excel, although I can do much more in word.
I have just replicated your query and found the easiest option after creating the first row, whereby you have your row height and column widths configured as you want them. I merged four cells horizontally then copied that merged cell into what would be the first cell of unmerged cells in the required rows. This then transformed four adjoining cells into one merged cell.