Titan Heart "Not in Range"

[Atreides]

You don't need to actually attack the heart, you'll still be hitting Titans body.
Just target the heart and attack him like usual, it might be a little difficult since there is no circle to indicate his hitbox but you'll get used to it.

[Swarna]

Stand further away. Trust me. You can for some reason hit him way more easily with more distance. And the max distance allowed on this part is jarring.

Also, the flank and back on Titan's heart seems to be dependant on who is aggro'd on. Stand across from the person with aggro for the back attack, and perpendicular to them towards Titan for the flank attack. If you do all of this you'll ensure your combos go through with fluidity.

[mr_wazzabi]

You don't need to actually attack the heart, you'll still be hitting Titans body.
Just target the heart and attack him like usual, it might be a little difficult since there is no circle to indicate his hitbox but you'll get used to it.

This. I just pretended to hit his body and they registered. If you try to move into visual striking range of the heart, you'll miss. Pretend the heart is not there and attack as usual