Issue releasing a new version of an app on Flathub

Has something changed on the way that a new version of an app should be published?
For many years all I had to do was to push some changes to the master branch of this flathub repo, but now doesn’t seem to work anymore.
Before the PRs use to be built automatically, now they are not:

So, has something changed recently and how can I publish a new version of my app?

I see a successful build from master. What’s the problem?