Lets say I have two branches A
and B
(A)--------(A+B)--------------(A+B+R)
\\ / merge \\ revert /
\\ /
You need to revert the revert, i.e. revert the commit that your previous revert created.
The reason for this is that a merge really does 2 things: it changes the file contents to reflect the merge, and also creates a commit with 2 parents to tell git what was merged. When you revert, it undoes the first thing, but not the second. So when you try to re-do the merge, git has no idea that you reverted the previous merge, so it ignores everything before then.