When I started, this was the state:

• No "development" branch selected
• No "production" branch selected
• Bugfix, Feature, Hotfix prefixes chosen

At first, I tried to only set the Development and Production branches, and then check the "enable automatic merging" checkbox. When I clicked Save, the two branches were saved, but the checkbox for automatic merging was unset.

I then tried just checking the checkbox again, and clicking Save, and it still didn't work.

Then I tried enabling the Release branch prefix, checking the checkbox, then clicking Save. That seemed to work.