Switched from Giant (Stans) to Muc-Off this year and I love it. If your sealant isn't able to clog a 1mm hole, I'd try another one.
Have you checked to see if the object that caused the puncture was still in there? Might sound silly, but it happens sometimes. You may just have been bad lucked!
Another option is to unmount the tire at patch it from the inside properly.