I have used this plugin on 2 other blogs without issue. On an older blog that I am reconfiguring, one with 10,000 posts. I am trying to have posts that were formatted in our older format /%category%/%postname%.html to this format /%category%/%postname%-%post_id%.html. When I activate 404 redirect, based on how it has worked on other sites, it should auto redirect the old url to the new one and report it as an auto redirect. However its just loading a blank page.
I have tweaked the permalinks and disabled all plugins to try to see if that affected it.
Thanks in advance