Hi, Alberto,
I found ART can not read some mono channel TIFF files which were edited with GIMP. I attached sample files. Other file viewers (like Irfanview or XnView etc.) or Photoshop can read these files.
Any advice please.
Regards.
https://drive.google.com/drive/folders/1FZ4Y7JffQPza58PnGkp7xexa0wreiPW4?usp=sharing