Gitlab with Jenkins

Hi All,
I am using gitlab ce 13.12.15 currently.
Earlier I was using gitlab ce 9.0.1 with Jenkins and it was working fine but when I updated gitlab to latest Version I am unable to automerge release branch to master although automerge working for develop to release.
When I did some debugging through git bash it shows nothing to merge although there were many commits to merge.
Please help me on it.