An error 500 comes out when I try to connect my jira with self-host gitlab

I download an app called GitLab for Jira to connect the jira with self-host gitlab.

It works for a month but recently it returns a 500 error when I tried to add new repository into my jira

I have no idea how to debug this error and find the root cause as I cannot find any error message in log system

Anything changed on jira side? ssl cert changed? plugin licence issue? jira licence issue? network issue? Which logs are you referring to when you say you cannot find any error message?
check jira logs, /var/atlassian/application-data/jira/logs
check atlassian-jira.log file, maybe there is a clue there