Tascam DM3200 - Assigning Function keys doesnt work

Hello,

I use a Tascam DM3200 as Remote control and automation.
Basic Function are working fine, using Mackie protocol.
But if I want to assign the F1 - F8 keys in Nuendo from the Tascam Control panel,
it doesnt do anything at all.

Ayn idea?

Thanks

Symon