I always like to redirect anyone asking about re-vegging to a post Cap made. It perfectly demonstrates what happens in the Re-vegging process but I will explain it anyways.
When Flowering is initiated The plant generally streches a foot or two, opening up space for buds etc. At that point the same growth hormones that are realeased when topping begin to be released. Small branches for each bud are created and thus the bud is created. This is better demonstrated in some more pure sativa strains, but the process is the same none the less. So the point I'm trying to make. Is that a lot of re-vegged clones will have some crazyyy branching. I've witnessed it, but caps picture blew my mind :p.
Taking clones from a flower plant is something you should only really do if you are preserving genetic lines. Clearly you are. It Can take about a month for a re-vegged clone to root. It can also take the normal amount of time. Something this late into flower will most likely take a pretty long time, be patient, dont pull it out of your cloning tray super often. Just let it kick it.
I just realized you said it was around Day 40. Do you not have visible roots? The plant will do more re-vegging after the clones have taken root. It can take a long time though so dont be disheartened. From your pictures the clone looks pretty healthy.
Good Luck,
Chobble