For the last few weeks, I’ve hardly been using the Mac Pro, as I’ve been avoiding coming to sit and work at the desk, favouring working from the laptop in the lounge in the brief periods between renovation work on the house. I needed to do some advanced iPhoto Library manipulations, and therefore found the MacBook to be somewhat underpowered, I came and started using the Mac Pro again. Obviously after a few weeks away, there were some system updates required, as well as other app software and notably Pages, Numbers, Keynote and iPhoto from the Mac App Store. I launched into the App Store and went to the Updates page, but got the message “Cannot Connect to App Store”. I tried several times, restarted, came back to it later in case it was App Store downtime, but to no avail.
After hunting around and trying several suggested remedies, all to no avail, the following process resolved the problem for me.
1. Close the App Store (make sure to Quit)
2. Open **Keychain Access** from the *Applications > Utilities* folder
3. Click on **System Roots** on the upper left panel
4. Click on **Certificates** from the lower left panel
5. Scan through the list of certificates on the right and look for any with a blue “+” symbol overlaid on the icon (these have custom trust settings, which might be wrong).
6. For some reason just setting them to **Use System Defaults** doesn’t make the settings apply, so repeat the following steps for all certificates with the blue “+”
7. Double Click on the certificate to show the info panel
8. Click on the triangle next to **Trust** to reveal the Trust settings
9. Change the **Secure Sockets Layer (SSL)** setting to **No Values Specified**
10. Close the info panel, you should be prompted for the administrators password.
11. Double Clock on **the same certificate** again
12. Expand the **Trust** settings
13. Change the **When using this certificate** setting to **Use System Defaults**
14. Close the info panel, and again enter the administrators password.
15. Repeat this for all of the certificates with the blue “+”
16. When done, restart the App Store and see if you can access Updates.