Wireless: 'fixed role not available' displayed in CellCom or FSII Belt Pack window
'fixed role not available' usually means that another beltpack has already connected using that slot or role. So either pick another role or deselect that role from the other BP as a static role choie
For the older CellCom 10 there are only 10 fixed roles. You link a pack with a role be registering it to one of the slots.
It could also be that the map has gotten corrupted.