Developing connect app

Question

Trying to establish a cloud instance that I can use to dev/test myapp

When I try uploading I get this unspecific, unhelpful error message:

(my connect json via ngrok) "cannot be installed on this Cloud instance."

How I am supposed to know WHY it failed and how can I work out WHAT to do diagnose.  I have looked at others examples and they don't help.  BTW this worked fine a few months ago.  I have spent over an hour registering a new domain name, creating a brand new atlassian jira software instance, just in case it was because I might have previously installed the app via the marketplace.

Admin Story analyser at projectsizer.atlassian.net · Answer

Conclusion was that something seems to have changed in the last few months with the way Atlassian reading connect documents.  I needed to forced the http header to set doctype = json and it gave it a .json suffix.  All fine now, i hope this helps someone else.

Colin Hammond_fqolx3 · Answer

For the reference of Atlassian folks, my development is completely blocked by this problem.  A fast response would be most welcome.