Invitation 'Accept' button not working

[codinghorror (Jeff Atwood)]

I’m not sure, do you see anything there @dax? The error message isn’t great. It could be this recent problem related to duplicate user prefs in the database:

User cannot signup due to duplicate values in category notification states

Hello Members can’t sign up to the site. This has started 11 days ago and no new users have been able to join the site ever since this was reported. Here is the logs I’ve found for this. [discourse%20error%201] A little note: We have migrated Vbulletin 4 database like 2 months ago to discourse. We never encountered this problem before. Any help will be highly appreciated. Thanks

Do you see any relevant errors in /logs when logged in as an admin?