Thanks for bringing to my attention. Looking back at my email, this same thing happened in September 2019 when we upgraded Confluence to 6.15.9. It broke again with Friday’s update to Confluence 7.1.2.
I have emailed the app developer to ask for information. Long term, we may need to find an alternative means of rendering these.
The UML diagrams should all be functional again. The app author prompted replied with an update that I applied to the server. (I get the feeling we’re one of only a few organizations using this rendering app.)
There are two pieces to it: authoring and rendering. UML Sequence Diagrams are a standard so I believe we could move both/either to another platform. It seems the rendering of the diagrams is where the current problem lies. I could look into alternatives for that and keep the authoring on the same site.
For the openIMIS wiki on Atlassian Cloud we experimented a bit with the PlantUML macro. It looks quite stable and can also do other graph types e.g. graphviz, salt. PlantUML syntax is quite standard: