Can't convert APNG file

[barnaclebarnes]

I have an animated PNG (see attached)

Using the latest XnConvert from the Apple App Store and on the latest version of Mac OS X High Sierra.

When I open the file and try to run any conversion (say to Webp) or just add some effect it only exports a single frame. It doesn't keep the animation.

Any ideas of what could be going wrong?

Thanks
Glen

[xnview]

XnConvert convert only images not animation like APNG/GIF