Yep, I can eat a 100mg edible and feel nothing, 200 mg maybe a little. 300mg I'll probably be passed out.
Once I bought a 1g tincture of "pure" THC (no other cannabinoids or terpenes) and I could take like 300 mg of it and feel a slight high, kinda like a bit of "brain fog" but nothing near like what smoking or doing edibles does to me. It must have something to do with decarboxylating the weed and the "entourage effect".
I hear some people are "immune" to THC edibles. Consuming them with something fatty, like peanut butter, might help. I personally like live rosin edibles. Got all those cannabinoids working together. 👌
I am one of those people, unfortunately. I've eaten hundred of MGs of stuff bought at legit sellers from Colorado and California, and nothing works. The only time it ever worked kind of was when they were home made brownies using the cannabutter method using an absolute ton of leftover flower to get it strong enough. I've been told it's an enzyme thing most likely.