On the Apple Device
Setting > iCloud Find My iXxxx
Turn off the Find My iPhone or iPad ....
Use the newest password for the changed ID
If that fails
Setting > iCloud Scroll down to the bottom and Sign out, or Delete the account
Use the newest password for the changed ID
If that fails
Turn off Find My iPhone Activation Lock - Apple Support
If that fails
Get signed in with you Apple ID/iCloud account and password at iCloud.com
Select the Find My iPhone
Select the "All Devices"
Select the device
Wipe and remove it from the account
Restore the device
This will wipe the device and you will need to setup as "New"
Best of Luck