Do these struts refer to the ones that help the hatchback go up and down or is this the power arm?
The part that broke is the one that would have been here in this picture:
View attachment 314912
That one locked up when all of this happened and I had to detach it. The motor wasn't moving or something else went wrong, all I know is that when the button was pushed nothing would move and I couldn't close the hatchback trunk at all, nothing would move. Unbolted it, it fell into the hole there never to be seen again. We are able to manually open and close the back there with no problems now that it is off.
First, no matter what, Get new struts at rockauto or Amazon for like $20 each. I've bought from both. That way the manual open/close will be alot lighter and easier to open. Once the power liftgate is fixed, the new struts will also ensure it doesn't strain/break the motor. You don't want to fix/replace the power gate only to have it break from trying to lift all the weight by itself. Replace the struts.
Even though CX9 are rare, not too many people want/need that part.
Go to junkyard and get the part you broke/lost for cheap like $20 or less. While there, notice how everything with the lift gate and motor works.
Did those older models have a reset function? If so, try reset
Check your fuses.
Make sure the actuator is working.
Also check the liftgate motor and make sure it's working.
The actuator, motor or fuse could prevent it from closing.
You can get actuators and motors from junkyard for cheap.
Depending on the junkyard, you may be able to accompany them. Tell then you want to see if it's similar to yours.When they pull it ,you can watch how they take it apart. A few hours/weekend of your time will save you alot of $$$. Dealer will probably want a few thousand to fix.
Worst case scenario disconnect the power motor permanently.
Put on new struts and maybe use a junkyard actuator if yours is broke. Then just use manual open/close. Save all that cash for newer used car or new car.
Oh and the struts are the black gas tubes with blue sticker on them. There should be two.
EDIT: also to check the lock actuator, lock your car using the keyfob or front door buttons, see if the liftgate locks and listen for it to click. Likewise, make sure your keyfob can unlock the actuator as well. If it's lock and unlocking then your actuator is ok .