no output file from compiled gui

Hello, I created (in matlab 2015b) a gui that performs some fitting and in the end creates output text file with parameters, the source code of this part is more or less like that:

[fn, pathname] = uiputfile('*.par', 'Name output *.par file');            
FID =fopen(sprintf('%s', fn),'wt');
fprintf(FID, 'headers\n');
fclose(FID);
save(fn, 'parsmono', '-ascii', '-append');

The gui works fine in matlab, but stopped after deployment to windows standalone app. There is no output file after performing the operation, however it seems as if it was created and deleted afterwards. Running app as an administrator didn't help. The problem happened on two computers, on two others it was fine. Do you have any suggestions what may be wrong?

Answer 1

[Jan]

Do not omit the important pathname:

[fn, pathname] = uiputfile('*.par', 'Name output *.par file');
File = fullfile(pathname, fn);
FID = fopen(File, 'wt');
fprintf(FID, 'headers\n');
fclose(FID);
save(File, 'parsmono', '-ascii', '-append');