icloud backup ipad

I have the message on my ipad " icloud backup. This ipad hasn't been backed up in 3 weeks. Backups happen when this iapd is plugged in, locked, and connected to wi-fi." I have plugged it in, hooked up to wi-fi, but nothing. The message never goes away and I can't do anything on the ipad. Any help would be great, thank you.