We are using Jira plugin on Jenkins to comment on Jira issues about build status. Since we have not done any infrastructure changes on 17th and 18th I suspect some Jira update caused the official Jira plugin to fail with the message as below:
ABC-1234 issue doesn't exist in Jira
To be sure I updated Jenkins along with all it's plugins to the latest versions, re-generated API key for the user in question - it made no difference.
Using curl/postman I could successfuly query the issue details by directly requesting from the API. Changing the Jenkins JIRA plugin issue selector regex to the default one (replacing empty with regex suggested in help) did not make any difference.
Captcha error response header is absent in the response to API call.
There are at least 2 known users reporting this problem - Jira community