It seems that a WordPress upgrade at some point this year put WordPress-with-Blockline into an inconsistent state.
I worked around it by changing the theme back to Twenty Twenty Three, using my host’s WP management software. (I guess there is some way you could do this over FTP too.) Once I had changed the theme, I could log in as admin, and the first time I logged in as admin in that state, I got a warning about allowing a WordPress database upgrade to proceed automatically; I allowed it, and once that had completed I was able to simply change the theme back to Blockline.
So something about that intermediate state of WordPress broke the mechanism that Blockline infers the URL. Not really Blockline at issue there and I guess there’s a lesson for how WordPress manages breaking changes in here.
