Crew has changed several times. In 2019, Eric Boe was replaced by Mike Fincke, due to a medical issue. Mike Fincke was supposed to fly the CFT mission with NASA rookie Nicole Mann and veteran Chris Ferguson (a crew of three).
But then Chris Ferguson quit being an astronaut citing "family issues", so they were down to two.
Then both of them were replaced by Sunita Williams and Butch Wilmore. Not sure what happened with Mike Fincke, but I recall that newbie Nicole Mann had some "personal issues" for a while and was reassigned.
Lots of crew changes on this thing over the years as it fell further and further behind and over budget.
Hope it can fly - safely - soon.