Cannot open any https sites or use SSL apps

try MTU 1200

First, the process by which OS X checks the validity of root SSL certificates doesn't currently work behind the authenticating SOCKS proxies used on some enterprise networks. If applicable, contact your network administrator. The proxy server may need to have its settings changed.

Disable the built-in application firewall, if it's in use. If you're running a third-party firewall such as “LittleSnitch” or “Hands Off,” disable that. Test.

In some versions of OS X, Parental Controls has a bug that prevents loading of secure websites. Turn it off.

Are the current date (including the year) and time shown on your system clock? If not, correct them and test.

Otherwise, launch the Activity Monitor application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.

Select All Processes from the menu in the toolbar of the Activity Monitor window, if not already selected. Enter "ocspd" (without the quotes) in the "Filter" text field. Is a process with that name listed?

If not, select Go ▹ Go to Folder from the Finder menu bar. Into the text box that opens, copy the following line of text:

/var/db/crls

From the folder that opens, move these two files to the Trash:

crlcache.db

ocspcache.db

You’ll be prompted for your administrator password when you do this. Then reboot, empty the Trash, and try again.

This is an HTTPS site. How are you connecting to it?

Is the iPad on the same network as the Mac? Not on a cellular network?

Please read this whole message before doing anything.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards. Boot in safe mode* and log in to the account with the problem. The instructions provided by Apple are as follows: