I uploaded a connect app in jira,but the app is not opening

I created a an app using json,python-flask,html, the app is perfectly working when I am opening it in browser,but when I upload the app in jira,its getting successfully installed but its not opening at all.In the inspect page it is showing “Failed to load resource: the server responded with a status of 404 ()”,and in the app page its showing “something gone wrong”.Can anyone please tell what is the problem,should I install any dependencies while using python flask