try flashing back to stock sprint rom and seeing if it works? The flashing part isnt all that hard if it is already unlocked.
But it might be that the touch pro 2 you bought had verizon's radio installed on it? not sure how to tell this though...
Another case that happens when I activate phones is that you need a hard reset to provision it again to sprint. cab is here, downlaod and install it
http://forum.ppcgeeks.com/htc-touch-...ml#post1541056