The Proxy is showing as Health Warning or Critical because of the Cachepulse license. The license shows up to date on Configuration > Proxy Settings > General > Cachepulse (at the bottom), and shows up to date under Maintenance > License.
Cachepulse does not update in the health checks, until it has downloaded a new update which will only occur when there is new content (This can be weeks at times.) or when first enabling it.
Enter user name and password
devicename> enable
Enter your enable password
devicename# config t
devicename(config)# cachepulse
devicename(config cachepulse)# purge Note: (The purge command not present in the CLI Guide or via ? command)