First thing I would do is look around for a shut off valve leading into the house. Sounds like someone's turned it off. Gardeners will do this sometimes.
I had a similar issue when I installed my system. Make sure the water is turned on at the master valvue...then go to the kitchen sink and unscrew the faucet head and turn the water on. I had dirt in my lines. I slowly let it leak out until it was back to full pressure.
Also had to go to the toilets and in the back of the toilet pull the tube that puts new water into the bowl out so it does not refill the bowl but refills the back. I saw dirt and other particles in the water. Flushed about 5 times at ALL toilets until I was sure all the dirt was out of the lines.