In
page 14 of the Global settings (accessed by pressing Edit Select then Bank Right/Global), make sure that Midi Prog Sel is On.
For multitimbral operation, why not use the first patch in the user bank (the one named Multitmbrl) if you haven't overwritten your user bank. Alternatively, you can edit any user mix to be 16 part/channel multitibral by going to mix mode, then Edit Select followed by the 90 button.
Page 1 should read Midi Input and it should be on for all 16 channels. You have to set each channel individually. Pressing 0-9 then 00-50 steps you through the 16 channels in the mix. Also, in the same mix edit mode, pressing button 60 will bring up the Prog Enable page; all 16 channels should be on for all 16 parts to be usable.
Best,