Find out exactly where the leak is. Fill a spray bottle with a mixture of soap and water and spray it liberally on the zorb ball along the seams. You will notice that the solution starts to bubble up where the leak is located, so take note of the position the hole.

And then, Prepare the hole for patching. Dry the seam off, and make sure that it is completely deflated before attempting to patch the seam. If you have the patch kit that came with the zorb, you can use the prep solution to thoroughly clean the rubber before proceeding. Rubbing alcohol also works. Apply plumber's goop liberally to the seam and let it dry for about 15minutes. If possible, apply some goop to the inside of the seam as well, so that it spreads out and gives an extra layer of protection when the zorb pressurizes.

Finally, Fill the zorb ball about halfway with air and wait another 30minutes or so to make sure that the goop has dried completely. Inflate the item completely and spray it again with the soap and water mixture to make sure that the hole is indeed fixed.

 
Any ideas or question, just feel free to let me know!