NMoasis said: Possibly one or both of a couple things concerning the roots. It definitely hasn't established itself, time for some detective work:
The soil it came might be hydrophobic and repels water from the roots when you water it. Dig it up and see what's going on in the root ball. Stick your fingers deep into the center to see if it's damp or bone dry in there. Might also be root bound; did you loosen and spread the roots when you planted?
Or, the youngish roots are having trouble getting established with the competition from surrounding plants and trees. When the other hibiscus was planted 10 years ago, it didn't have so much competition and was able to establish more easily. Dig down there and take a look.
Did you water daily when first planted? Have you fertilized? Used soil amendments?