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Most probably, you need to reset your Jira instance settings. Please check the following article that may help to troubleshoot an issue:
https://confluence.atlassian.com/jirakb/not-receiving-emailtroubleshoot-notifications-in-jira-cloud-779160705203394737.html
We’re migrating from Jira Server to Cloud. Can we have our trial period extended for Smart Checklist for Jira Pro Cloud?
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