Yeah, I did the same dumb thing about last week. I was looking for a diplomat to do a specific Doff mission. I found one that exactly matched the success and critical success requirements perfectly. I bought the Doff for 250k EC. Turns out the Doff was for the KDF faction, not Federation. I bought a less expensive Doff (200k ??) that was a close match, but one of the traits for a critical success was different. I put the KDF Doff back on the exchange for the same price I paid. I took a little over a week, but I eventually sold that Doff.
At the bottom of the Exchange screen there should be a radial that you can click to restrict the Doffs that are valid only for your faction. That way you do not accidentally buy a Doff meant for a different faction.
More recently, in fact just yesterday, I saw a Doff mission that would give my ship a permanent buff to accuracy for energy weapons (if I remember correctly). Since I only had maybe two energy weapon officers of green quality I hit the exchange to find a blue quality Doff. I eventually bought a blue quality Reman with efficiency (the only one unless I want a purple Doff for 5 million ECs) and another two traits I was wanted, but not absolutely necessary, for about 370k EC.
Cool all set... took only about 5 minutes... went back to the Doff mission... and it was no longer there... I guess the missions got rotated....
Doff missions in sector space refresh every 4 hours, department head refreshes I think 20 hours, and personal tab is 1 hour. Theres a timer for sector and personal so you can plan things accordingly
Comments
Did you check to make sure the Doffs were of the same faction as you are before you purchased them????
(It is possible to purchase Doffs from a different faction, however, they are not usable for your own assignments...)
Uh...err... *cough* I forgot to check ... so used to buying commodities. See I KNEW It was something obvious.
I'm sure that was it - lesson learned.
Anyhow, as suggested, the most common reason for this is the duty officers are of the wrong faction.
Red border around the doff's picture means it's KDF, green border means romulan, and blue border means federation.
To the OP, what color border does your doff's head pictures have and what faction are you?
At the bottom of the Exchange screen there should be a radial that you can click to restrict the Doffs that are valid only for your faction. That way you do not accidentally buy a Doff meant for a different faction.
More recently, in fact just yesterday, I saw a Doff mission that would give my ship a permanent buff to accuracy for energy weapons (if I remember correctly). Since I only had maybe two energy weapon officers of green quality I hit the exchange to find a blue quality Doff. I eventually bought a blue quality Reman with efficiency (the only one unless I want a purple Doff for 5 million ECs) and another two traits I was wanted, but not absolutely necessary, for about 370k EC.
Cool all set... took only about 5 minutes... went back to the Doff mission... and it was no longer there... I guess the missions got rotated....