HISE can't load soundfonts. It can load flac and probably aiff but generally it's best to stick to .wav and then convert them to .ch within HISE. It can also import the mapping data from SFZs.
@d-healey hmmmm. not going well. Firstly velocity is optional in my project. Secondly with an arp it continues playing, and thirdly even in a button it doesn't reliably call the waveform... at least not in this project