/tp entity to entity not working

Please add the exact commands you used.
If you summoned the PrimedTnt without a fuse tag, it'll explode instantly, so it can't teleport.

Exact command for TNT summoner command block:

/summon PrimedTnt ~ ~8 ~ {fuse:3}

First a command block with

/testfor @e[type=Arrow,r=50] {inGround=1b}

sets off a comparator that powers a command block with

/tp @e[type=PrimedTnt,r=15] @e[type=Arrow,r=50]

Everything is typed perfectly as far as I can see... And I can see the comparator from the arrow in ground command block turning on and powering the tp command block.

Now that I think of it... It might be a bug with the fuse tag.

I think that your error is that you have to write

{Fuse:3b}

@e[type=Arrow] is not allowed (there can be multiple arrows in a world) use @e[type=Arrow,c=1] (detects the closest Arrow)