First of all: I am not 100% certain that Imagemagick is correctly installed on my host, since I don't have root/ssh access. BUT: Your plugin gives me the green checkmark next to /usr/bin as a path, so I assume it should work.
1. When I click on the button to regenerate all images using Imagemagick, it starts processing and finishes with telling me how many pictures it has processed (there are no error messages). But, the pictures in my wp-contents/uploads/ folder, remain unchanged.
2. When inserting pictures into posts all resize options are greyed out. But again, there are no error messages to be seen anywhere.
Any ideas what could be wrong?