My pedigree was replaced by a wrong couple as my grandparents. I removed them from being my father's parents, but I still can't restore my tree upon opening my account.
I am just another 'lowly' User/Patron ...
Just in passing ...
Go to the "ChangeLog", of you Father.
Look through the "ChangeLog", of you Father, to find, the ORIGINAL Parents, of your Father.
Once, you have found them, you should be able to either, "Unmerge"; or, "Restore", them.
Here are some "Knowledge Articles", in 'FamilySearch':
I hope, that this/these may help/assist, somewhat.