Advanced Call Forwarding won't open!

I'm trying to set the number of rings before the voicemail picks up and for an hour all I keep getting is:

"Sorry,

Unable to process your request. Please try again."

I tried everything including resetting my PIN. I only have one phone, (a corless home phone). No cell, and no other communication devices. I switched the base unit's phone line to the other telephone jack, tried again, and then put it back where it was. 

I just keep getting the same "Sorry..." message.

Rich