Pull request with branch does not exist on server: release/1.1

I’m using SonarQube extension for VSTS version 4.4.
Trying to analyse a PR being pushed to our release branch “Release/1.1”.

While analyzing the PR code changes, I keep getting the following error:

2018-11-06T22:21:05.1594219Z ##[error]ERROR: Error during SonarQube Scanner execution
2018-11-06T22:21:05.1594877Z ERROR: Error during SonarQube Scanner execution
2018-11-06T22:21:05.1597014Z ##[error]ERROR: Pull request with branch does not exist on server: release/1.1

We are running SonarQube 7.3 Developer Edition.