My bet is the valve is faulty or installed backwards if that is possible.
About the only thing I would recommend before heading to the dealer is to take that valve out of the system and see if you can blow and suck on the line to the tank with no valve in place. Call the service manager at the dealer and explain the issue and ask if they will still honor the warranty if you pulled the valve off for basic troubleshooting before making the two hour drive.
Or ask your RV mechanic friend if he has the PEX crimping tool you can borrow. If so then cut the crimp bands off and check the system. If you figure it out great. If you can't figure it out, put some new bands on the joints and pull it to the dealer.
