Just read up a bit on THC lean. It could possibly be that the bud used for the lean wasn't decarboxilated properly before made into the liquid, in other words just a bad batch. THC lean is apparently supposed to affect you much quicker than any edibles because it is a liquid, and some sites even warn you of using the correct dose to prevent any overwhelming affects, so if you're feeling nothing after using the prescribed dose then there is definitely something up.
Could maybe also be that weird scenario where it doesn't work for you but works for someone else

has anyone else given it a shot with you?