Does not add next images

[adrianoaj]

It doesn't work, it just keeps the image of the first tiff file in the output file.

Any tips?

[Darkseal]

Are you sure you're using a multi-page TIFF file viewer? Standard TIFF viewers will only show the first page (i.e. the first TIFF file).

Here's what I'm using to test my app:
https://www.irfanview.com/

Can you share one of those "merged" images where you only see the first page?