I had a leaky shower head so I decided to change the seats and springs. I have a Delta Monitor 1700 series. Easy enough I thought. I got the seats and springs changed and put the cartridge and everything back together, turned the water back on and now nothing. Just a trickle comes out of the Shower Head. Any suggestions would be great.

In replacing then seats and springs sounds like you loosened some minerals built up in the pipe walls that are now blocking the inlet ports.
Shut the water off and remove the seats and springs, Check and clean the inlet ports. Now turn the water back on to flush out the supplies. Reassemble and test. Better now? Good luck, Tom

... Or you didn't assemble the faucet he way it was before. I suggest that you disassemble it and assemble again. Pay attention what you are doing.

I suggest that you disassemble it and assemble again.
In case Milo's correct, this may help, (see image) Good luck, Tom