GWG, I've removed the prior version and reinstalled d5b91a0. I don't get the same original notification (I'm suspecting because the original stored a value in my db that unflags the nag). However, when rerunning the diagnostic script at /wp-admin/admin.php?page=indieauth I get the same positive response that "Alternate Header Found. You should be able to use all clients." Sadly, I'm still getting the same old 403 when attempting to log into Monocle.