Sounds as though the valve was not properly installed. Did you remove the entire assembly? or just the internal workings within the diverter valve itself?
If the valve did not work before you fixed it and nothing has changed sense you did the repair, I would be looking for a blockage somewhere between it and the shower head. Have you recently changed the shower head? Perhaps the gasket that used to prevent it from leaking has shifted and has blocked the water flow from entering into the shower head itself.
You may want to remove the shower head and try running the water again. Does the shower head have adjustable spray? Perhaps as dumb as this may sound, Is the spray head turned off?
Woodbridge has asked some great investigative ?...we need a bit more info
Thank you all for your replies, however I determine that the problem was beyond any repair that I could make. I contacted a plumber, found out that the entire assembly will have to be replaced.
Yes, he also tried replacing the valve, the water did not flow through the shower head. It continued to be a steady stream through the bath tube spigot.
A three handle shower assembly with the common center valve being the diverter valve can always be fixed unless they messed up the threads of the seat. Then the whole faucet would need to be replaced. As all the parts with exception of the brass fixture that connects the pipes is replaceable.
The seat assembly can be removed and changed, along with the entire handle assembly.
Sounds as though your plumber is trying to over sell you something you do not need.
not all seats can be removed, for minor damage they can be "faced" with a dressing tool...for the one that are not replaceable and beyond "facing" a wholesale replacement is needed.