My guess is that your firewall is now blocking calibre. Did you recently get a new "security suite" or antivirus program?
Try going through the steps listed in FAQ 1 of the post Calibre Companion Android App: Information, Change Log, and FAQ
. The FAQ assumes you are running windows and windows firewall. When going through the steps, be sure to interact with the firewall that is actually installed. For example, ESET seems to block calibre by default, so you will need to do whatever is required to change its settings, not the windows firewall settings.
If you can't resolve the problem, then:
1) What IP address does calibre display in the Connect/Share menu for the content server and for the wireless device?
2) What IP address does CC display in the settings for wireless connections?
3) Can any other computer/phone on your home network "see" the content server?