RTK with copter 3.5

I have a Here+ and had it running RTK on a cube 2.1. The cube crashed and I got no answers as to why so I want to put the Here+ on a pixhawk with copter 3.5. After plugging the Here+ in to GPS, Ic2 and the safety I get only a 3D fix. Mav is running and so is the base but I can’t get it to go to float??
I tried the baud rates for gps & mav but it does not change anything.
Will RTK work with 3.5? Does anyone know what parameter to set?