Then you need to go to your profile on backer portal:My accounts were linked by Infinitron giving my email to Owlcat. I already had an account at their forums created with the same email from my paypal, which I used when donating through the codex fundraiser.There is whole instruction in your mail. You need to link accounts.
I had to change my password for the forum, and my email already existed in the database of users.
https://wrath.owlcatgames.com/preorder/profile
And link your backer profile to Owlcat's forum profile by nickname
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PS yes, it is more contrived than it should be.