Logging in to like on a site's post results in private page error

[Addison-Stavlo]

From p58i-ijO-p2

The log-in flow to like sometimes results in a private page:

but logging in to like is completely broken and ends at “private site” screen (the blog was public):

I have not been able to repro this in testing and it seems to work for me so far. cc @simison if you have more info and are able to update testing instructions or bring in more details/context.

To Repro:

• Open a blog post in an incognito/logged-out window.
• Click the like button.
• Log in with an existing account in the popup window.
• maybe see private page error?