Using v2.1.2 with Gimp 2.8 on MacOS. Multiple filters produce essentially the same error:

*** Error in [filter name here]_preview/gui_split_preview
/*repeat/{...}/*local/convolve_fft/*repeat/*local/
*** Command 'fft': ClmgList<float>::FFT():
Specified real and imaginary parts (640,469,1,3)
have non 2^N dimension along the Y-axis

Any ideas?

The current version of GMIC is v2.2.0 Try using the current version and see if that helps.

Same result.

As far as installation goes, I simply added the 'gmic_gmp_ngtk' file to the plug-ins folder. Is there is another step or additional items required?

Try refreshing the filter cache.

Refreshed filters. Nada

Uninstalled GIMP. Fresh install of both GIMP and G'MIC. Nope, but the added bonus of having to hunt down all the brushes and scripts I once had :-(

This is a problem with the Gimp original mac built. I can only use libraries packed in the respective app.
Maybe slowly gmic plugin becomes respectable enough to be built into the original app?!?

Try using the bit outdated Gimp from lisanet with the plugin gmic_gimp_gtk or the Partha build.

I have no other recommendation, except to use macports or homebrew to build your own Gimp and gmic!

Thanks, karo03de. This seems to have solved the problem.