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
Enter your enable password
devicename# config t
devicename(config cachepulse)# purge Note: (The purge command not present in the CLI Guide or via ? command)