I can't merge certain cells in SSRS

There seems to be an invisible lines between the row headers and the data, and also the column headers and the data. You cannot merge across these lines.

The solution is to keep you groups and delete the row and column headers. You can put the header rows inside the data area and you can merge cells too.

Sometimes you can only merge the cells from a row if you merge the cells from the row above.

    _____1__________2_________3____    
A  |__________|__________|_________|    
B  |__________|__________|_________|    

Sometimes you can only merge B1-B2-B3 if you merge A1-A2-A3 first.

This problem occure with grouping. You cannot merge across group lines. I have not had a problem merging when there is not a group. There is not a way around this.