Hello @James Young
Thank you for reaching out on the community and telling us about your issue. Generally when you delete an account and you want to bring it back the best way would be to restore a backup. In your case I believe you added and deleted the account in a fairly small amount of time so there may be no backup to work with.
What financial institution were you adding from? I might recommend seeing if the the FI's website might have an option for third party programs where it will say you currently have quicken connected. If by chance it does you could try removing that connection so that you're able to try adding it again.
Once you get a chance let us know how it goes!
Thanks,
Quicken Francisco