I serviced the flowmaster, connected everything back up, opened the fill valve and the tank started to fill but locked with only an inch of water.
I disconnected the line to the tank and turned the water on... no water coming out at all.
What's up??

You disconnected the supply and couldn't get water past the angle stop?
Is this correct? Sounds like when you serviced the ballcock you disturbed some mineral built upon the pipe wall and now it's clogged the seat of the stop.
You're going to need a little help to do this. Shut the water off to the house at the house shut off. Open a cold water faucet to relieve the pressure.
Now unscrew the large nut at the rear of the stop and pull the stop away. Check the stop for any crud that may be in there.
Station a friend at the house shut off and you hold a large pan in front of the open pipe. Yell down and have him turn the water on, but tell him to shut it down on your command. If the water pressure expels the crud you're home free. Shut the water off and reassemble. If the pipe's still clogged take a small rod oor stiff wire and try to break it up. Turn the water back on for a second to flush the line out. This should get you back in business. Good luck, Tom

If you do as Tom suggest, you will most likely be good to go.