Polyphone reverses the assigned MIDI key ranges when Exporting an SFZ instrument file, which makes it non-functional in a DAW or SFZ player. Below is a simple workaround, but maybe Davey will issue a patch.
1. Open the SFZ file with a text editor.
2. Scroll down to the op codes for the samples and notice the instruction is to read the key range backwards. For example:
Yes, the key range for each sample must be corrected in a text editor in order to make the exported SFZ instrument file work, whether creating one from scratch or converting a good SF2 file to SFZ in Polyphone. The program is still nice. Hopefully a patch will be released or an update with the problem fixed.