In Appian, there is a limitation on the number of activities that can be chained in a process, known as the "chaining limit." If a process model exceeds this limit, which includes synchronous subprocesses and their nodes, the process may break or not behave as expected. In this scenario, with two large subprocesses chained from start to end, the maximum number of activity chained nodes could be exceeded, resulting in the confirmation screen not being shown. Adjusting the process model to reduce chaining or using asynchronous patterns where possible can help mitigate this issue.References:Appian Documentation - Process Model Best Practices