Unable to import shaders

Hello!

I am evaluating the HeavyM demo, 2.13.4 just downloaded off the website. When I try to import shaders I get "This tab can only contain Post-Processing ISF shaders, with a maximum of one input image" with every single one. I'm not sure what is meant by this, or why the one that goes get imported is ok and the others aren't. Any help would be appreciated!

Example:

https://github.com/sophiadigitalart/ShadersLibrary/blob/master/00100100.fs works but the rest do not