You've added custom fields to a screen, but yet they are not appearing for you when you create, or edit an issue.
Either
The simple solution - click "configure fields" to the top right of the popped up screen. There's a "where's my field" option in there which will tell you which of the problems you have.
You can use a Field finder to verify that is the problem. Please check this doc for more information.
https://confluence.atlassian.com/adminjiracloud/jira-admin-helper-818578850.html
The tool will tell you what might be wrong with your configuration.
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