Guitar Pro formats lacks backward compatibility which means it is not possible to produce .gp4 file using the latest version of the program. Your only option would be to find version 4 of the program and import .gp3 file to it so you can save it as .gp4 file. Without the required version of the program, this conversion is most likely impossible.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.
