Can't clone 1 perticular plant

So had a few random seeds given to me from a friend, handed down to them from another friend.
Out of the 5 seeds 3 have survived I also got some m-39 growing that paid for myself. I made cutting of every plant , useing heat pad / hudimity dome and clone-ex gel
This one plant that I really really want to grow again the clones keep failing and the other plants are cloneing fine.

Anyone else have encountered a problem like this? Any tricks of the trade I can use ?

I have run into the same problem about 5 years ago with a strain called El Monstre. Strange but stuff like this happens every once in awhile, first and only time I ever have had a problem.

i hear this often happens with hollow stemmed plants, they're a real bitch to clone. Check out air layering maybe that method can get you a clone.

Try without the dome or the heating pad or both.

My favorite strain takes close to a month to pop roots, but it's worth the wait and you just plan ahead.

Experiment a bit till you see what works.

Wet

Some moms need to be older to clone properly.

if none of that works aeroponics cloning has never failed me