Tricky.  A hot glue gun is not going to get it done and welding will likely spoil the powdercoat /plastic coating.  First, try and get a refund or replacement.

If you have no luck, you might be able to use a wire brush to remove a bit of the powder coating around the joint, weld it together and then use a spray can with a matching color and finish (gloss or semi-gloss) to cover up the join.  That will get you the strongest join, but requires the skills and tools. 

Otherwise, do a pin and glue joint.  Get a drill and a fine drill bit and drill a hole through both pieces at each joint location.  Then rough up the joint location with a fine file or sandpaper.  Apply some epoxy adhesive (high-strength two-part stuff) to the joint and pin the hole with some wire the same size as the hole. Spray paint as above to cover your repair.

Or just glue the joint (same method as above) and see what happens, that might be strong enough for your needs.  If not, try the pin and glue method.

Good Luck !