In order to debug the calamari connector, please:
turn on the logging https://your-jira.domain.com/secure/admin/ViewLogging.jspa for package "io.calamari" to debug
the next steps:
Turn on and off the plugin
Wait 15-20 min
Send us part of your JIRA log (/var/atlassian/application-data/jira/log/atlassian-jira.log) that contains "i.c"