We need to know what A actually is...just that it is present doesn't provide sufficient diagnostic data.
NB: From the documentation for XLSWRITE(),
"If A is a cell array containing something other than a scalar numeric or text, then xlswrite silently leaves the corresponding cell in the spreadsheet empty."
Also note that while you don't use it in the snippet above, your b12 is a single string in one cell, not two labels as it looks like you probably intended...
b12 = cellstr('Test input cell 1','Test input cell 2');
or, more simply written with "the curlies" as
b12={'Test input cell 1','Test input cell 2'};
