Anonymous Call Rejection not working

I couldn't remember whether Anonymous Call Rejection was on or off for my home phone line. I've used this feature countless times before, and I've never had a problem.

But whether I dial *77 to turn it on or *87 to turn it off, I now get:

"We were unable to complete your request. Please try again later."

What's going on, and how do I fix it?

Thanks for all assistance!