Options post Process Automation Instances Service Limits
Summary:
As per Administering Oracle Cloud Infrastructure Process Automation - Service Limits, the 'Maximum number of application versions that can be created per application' & 'Maximum number of activated application versions per application' is 25. We were able to create 50 versions for an app in development instance, and then Activation started to error out without any meaningful message 'Couldn't activate your application. Try activating it again.'
The application is live in production, but in development instance we deleted all previous version and tried to activate the app - but still same error persists. There isn't any code related issue as renaming the app gets activated gracefully.