Is your Mac up to date? If not, you could experience different issues such as secure web sites not fully loading or not being able to use certain apps.
To ensure you get the most out of your Mac, ensure you are on the most recent operating system, and that your operating system is up to date. For a list of Mac operating systems click here.
To check for updates on Mac OS click to view following Instructional Video or following the below instructions :
Tap the Apple icon in the top left corner and then tap "App Store".
Tap the “Software Update” icon.
If your OS is up to date you will not have the option to update. If you do need to perform an update you will see the name of the version you need. Tap "Update Now”.
The update will need to download in order to be installed. Once this has completed you will see the following screen where you will be asked to finish downloading the update and then restart. Tap “Download & Restart”.