Some assignments will prevent your Crew from undergoing certain basic Crew management operations, such as Upgrading (fusing), Dismissing, or sending them to Cryostasis.
When managing your Crew, if these options are greyed out, you should check the following locations for conflicting comittments:
-any active Shuttle Missions
-your active Voyage
-your Active Ship's battle stations
If you are uncertain which Crew members are assigned to your active Ship, please travel to a Space Battle in any Episode as if you were to play the battle; this will allow you to change your active Ship and Crew.
When Upgrading (fusing) a Crew member, you will also need to be mindful of the scenarios in which two Crew members can or cannot be fused. Two Crew members with identical names, neither of whom have reached their full Star Rating (indicated by the number of solid Stars versus transparent ones) can be fused, which will add one Star to the highest-quality of the two.
This means that you cannot fuse two Crew members who are essentially the same person but from different points in time, or two identical Crew members who are already at their maximum Star Rating. You also cannot fuse two Crew members with more than one Star each and retain the full quality of both; if you fuse two 2/4-Star characters, you will get a 3/4-Star version of that character, and not a 4/4-Star. When fusing multiple version of the same Crew, it's always best to lead with the one you want to upgrade to avoid a scenario where one copy is wasted.