There is a fundamental difference between Jira Server/Data Center and Jira Cloud: In Jira Cloud post functions of apps are executed asynchronously as a 'background job'. This means a post function will be executed after the transition has been completed on Jira Cloud.

Note the following behaviors of the asynchronous execution:

• If you are using multiple post functions, there is no guaranteed order in which they are performed. They might be executed in a different order from the one you set up in Jira's workflow configuration. Therefore, you cannot rely on any result of a 'previous' post function. Also, the order in which the post functions are executed might be different every time the transition is performed.
• If a post function encounters a problem (due to misconfiguration or the current data of a Jira issue), the transition (and all other post functions) will be performed regardless of the problem.
• The result of a post function might not be visible immediately in the browser.
• There are no error messages displayed to the user.