Hello @Emdw, and good to see you in our community. I bet this issue has been resolved by now, however my recommendation in this type of scenarios is to review the logs from any of the accounts aren't duplicate.
If this is not the reason then the next step would be to revoke the access of the third party app by going to your Application settings. Once you have done this, re-enable to link between your accounts.
Hope this issue has bee resolved by know, see you around!
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