Reach pixhawk 3DR+915Mhz issue

hi all
I have 2 reach modules, one as base, the other as rover.
The Base reach I power it a usb port.I use the GPS Inject function in the mission planner to transmit the corrections to the 3dr+915Mhz radio.
The Rover reach I connect it to the pixhawk’s serial4/5 port according to the emlid doc"APM Integration".Thers is a 3dr+915Mhz radio on the pixhawk tele-1 port.
I do the parameters setting according to the emlid doc"APM Integration",I am sure the parameters are all ok.
I flash the apm firmware provided by the emlid "copter-3.3.3 with ERB"
And I also set the 3dr+915Mhz parameters according to the emlid doc"APM Integration"
However when I use the gps inject feature by 3dr+915Mhz raido,I cannot get the grey bar in rover’s reachview.The rover is ‘single’.
when I set the rover’s parameters input source from wifi(Base’s IP),everything is ok,rover fix and we can see the grey bar.ON the mission planner you can see RTK status:5

can anyone help me, I try to solve this problem for 2weeks, but cannot make any progress.