price pfisher shower valve

i installed a new price pfisher shower vave when i remodeled my bathroom
got all the tile up and THEN tried to check it
well.........some water comes out for may 30 seconds then it just slows to a trikkle
no hot or cold
what could be wrong??
thanks

got it fixed
it was the sceen in the shower head was stopped up
didnt flush the system before i installed it