My 380 stopped working when the pressure relief valve blew. Have you checked that? Check the pressure relief valve attached to the wall, mine was shooting more and more water out the side until the unit did not move at all. I thought it was moving, but I'd throw it in and it would just roll downhill until it stopped. When I blocked the pressure relief port it moved a little. When it totally failed, I found a mysterious round disc in the pool. I should have recognized the Polaris logo but it was partially cracked where the connection failed and I kept looking at the parts diagram of the Polaris and couldn't find that piece...it is not shown as a separate part. Now that I replaced that, there is no water exiting that side vent at all. There was a mighty flow from it when the unit would not run.
The units are pretty easy to open up and take a look inside. If you trust that the pool store did in fact replace a bunch of parts, maybe it is not necessary. But, the mechanics of the thing is pretty simple.
It starts with the pump, of course, and so if it is not getting much pressure then internals of the unit won't work. Have you checked the pump basket? If it is clean, then listen to it, does the pump sound OK? Assuming you get good pressure and flow through the hose, and I did still get flow through the hose with the pressure relief valve blown but I had no way to know how that compared to normal flow for that, then the water goes through 3 ports inside. You can open the unit up after removing the hose and try to probe those ports carefully with a paperclip or something to see they are not blocked. Check to see all the hoses are connected.
One of those ports shoots water on the paddlewheel thing that drive the unit, so be sure that when that turns that the wheels do turn. I found it has some play in it that seems normal and that the paddlewheel turns a lot to turn the wheels a little.
Beyond that, you'll need to get someone else to help, I never went any further.