I cannot update or purchase any new apps. Each time I try, I get a message that says: '...failed to download Use the Purchases page to try again.' I get this message regardless of if I am updating or purchasing an app. I am STILL able to download and upgrade apple security updates, so my operating system is up to date. It is just third party applications that are the issue. I have done everything I can think of to fix the issue: 1. Sign out 2. Reset app store application (by enabling debug menu using terminal command) 3. Remove cache (the com.appstore file) 4. Remove any partial download files in /Library/Updates/ folder 5. Verify & Repair disk permissions in Disk Utility 6. Restart computer 7. PRAM reset 8. SMC reset 9. In security settings in system preferences, changed 'allow apps downloaded...' from 'anywhere' to 'mac app store and identified developers' If anyone has any tips that could fix this, I would greatly appreciate it. Thanks! Also note: This issue for me started in Yosemite, but has never been fixed. I don't have this issue on my mountain lion partition.