I purchased all of the same devices you have. Turns out you don’t need the Cooper remote!
The Minimote is capable of setting bi-directional associations:
- Enter association mode
- Press the master switch
- Press the accessory switch
- Exit association mode
- Enter association mode
- Press the accessory switch
- Press the master switch
- Exist association mode
You’ve already done steps 1-4, so you just need to do steps 5-8. This should solve your problem