I have been struggling with this for a while now. I've done many searches here in the PMDG forums as well as out on the web, but haven't found a solution yet. I am trying to operate a flight on -900WL NGX variant (PMDG United N75410) but cannot load a ZFW above 136.x, when I should be able to go as high as ~149.2. I use PFPX for my flight planning and it shows I should be setting my ZFW at 143.1. Whenever I try to add that value, I get the "Invalid Entry" message on the CDU. My NGX "Weight Units" in P3Dv4 are set to LBS and PFPX is set the same. The CDU will not accept a ZFW above 136.x with any of my installed -900WL variants, but all the other (-600, -700, and -800) variants work just fine.
I've searched PFPX, ZFW, PMDG, -900WL, Invalid Entry, in all manner of combinations to no avail. What am I missing? It's probably something obvious, right in front of my eyes, but, for the life of me, I can't see it.
Thanks for your time.
Edit: This is a brand new home-built PC (see sig) and a brand new install of P3Dv4. So everything is vanilla at this stage.