Wordfence on "[Plugin: Wordfence Security] Advanced blocking (IP range) broken in 4.0.3"

I find myself intrigued. I just modified my test machine to pretend it has your IP address. Then I blocked that range and it works great.

I pasted from your message:

198.27.99.0-198.27.99.255

without spaces prefixed or suffixed. Works great.

Are you running a caching plugin? Is it possible you're getting a cached message? If so can you clear the cache?

Try blocking a very slightly different range like: 198.27.99.0-198.27.99.254

and let me know what happens.

Not doubting your intelligence or sanity. Just a very curious problem.

Thanks.