If you happened to park your Orca at a station that does not sell Passenger Cabins, you will likely note you now have the option to upgrade your joke of a 4C Fuel Tank to a much more useful 5C Fuel tank.
Don't waste your time trying. You'll likely get an Outfitting Error.
Instead, take your Orca to a station that actually sells Cabins, and try to refit your fuel tank there. It will likely work without error.
I ran into this last night and this worked for me. Already been Bug-Reported, but if you're not wanting to wait, this workaround will likely work for you as well.
Don't waste your time trying. You'll likely get an Outfitting Error.
Instead, take your Orca to a station that actually sells Cabins, and try to refit your fuel tank there. It will likely work without error.
I ran into this last night and this worked for me. Already been Bug-Reported, but if you're not wanting to wait, this workaround will likely work for you as well.