Re: Blog permalinks suddenly start resulting in 404 errors
It was strange. I think I’ve fixed it now, but the disconcerting thing is that I’m not sure why what I did fixed it.
Here’s what I did:
Initially, I just deleted the broken subdomain blog and recreated it with the same title and subdomain as before (after I confirmed that my test subdomain blog worked fine). This failed however; the permalinks were still redirecting to the 404 page.
Then, I checked the database for artefacts after deleting the broken blog. In table wp_bp_user_blogs, there were two records remaining that contained the blog_id of the deleted blog. So I backed up the table and then deleted those entries.
Afterwards, I recreated the blog a second time. Now it seems to be working perfectly. But I don’t know why 
