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You will need to go into the user management and remove the "disabled" flag from the user you are trying to invite.
You can't invite them because they've already had access and hence don't need a new account, and you've flagged them as "not able to use this system any more", so you don't want to email them an invite, until you've re-enabled them.
👋 Hi there Jira Community! A few months ago we shared with you plans around renaming epics in your company-managed projects. As part of these changes, we highlighted upcoming changes to epics on...
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