There were recently changes in the Diaspora* protocol which disturbed the federated communication between the projects. To compensate the changes Friendica 3.4.3-2 has been released
How to Update?
If you have an installation using the git repository directly, all you have to do is a git pull in the friendica directory. That will fetch the new version from the master branch and you are ready to go. The development branch of Friendica 3.5 Asparagus, has been updated as well.
Alternatively you can find a zip file of the released version of friendica at github.com for download. Just unzip it on your local machine and replace the files on your server with the new files.