My knee just does not want to bend at all.
Of course not! Your knee has gone through some very, very serious surgical trauma.
Right now, your knee is still reeling from what the trauma that occurred, and it will take some time---possibly quite some time, for you to gain ROM.
Recovery---full recovery---can take upwards to a year; my own BTKR recovery took five months for me to lose a pesky little limp---six months to get to around 80%-85%, and eight months to get to around 90%-95%.
While you undoubtedly have quite a few staples, right now, the swelling and the stiffness are the major contributors to why your knee will not bend.
You are expecting, like many of us did, for healing to come around too quickly and too soon. Please consider that two bones were sawed off; your implant was not too gently placed in your new joint, you had tourniquets around two parts of your knee, and the surgeon and his helpers were not at all gentle. Then you were stapled shut.
These early days are called the "Dark Days" of recovery, and with good reason, too.
Hang in there, ice, elevate A LOT---and take it slowly---one day at a time.
You will regain the ROM, and you will be fully recovered---but you will get there on your knee's schedule, not yours.
It takes time and patience---this can be very frustrating, but you have to be very gentle with it---ice, elevate, rest---and do gentle little exercises.