Hi @Ara Cho ,
Thanks for posting and welcome to the community.
I hope you are aware of steps to integrate slack in Jira Cloud, if not please check these steps again and try - https://support.atlassian.com/jira-software-cloud/docs/use-jira-cloud-for-slack/.
I guess it might be some intermittent issue or some thing else(really hard to guess seeing these error messages and error id).
If it still happening again, could you please share steps you followed, your project type details here.
Looking forward for your response.
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