I asked Vaillant when my system would migrate to myVaillant. They said:
The sensoAPP and 700 apps are in the process of being upgraded to the myVAILLANT app on a new server.
The migration to the myVAILLANT app currently underway in batches and will be phased in by invitation only.
The app migration should be complete by early 2024, basic system setups first and complex systems (including ambiSENSE and 700 systems from late January to March 24).