SharePoint 2013: Product Configuration Wizard stuck on task 9 of 10

1. Delete the SharePoint Products Configuration Wizard dialog.  Terminate the process of necessary to remove it.
2. Open the Services.msc panel, and then look for the SharePoint Timer Service.
3. Stop this service.
4. Open Windows Explorer, and then navigate to the cache folder at:C:\ProgramData\Microsoft\SharePoint\Config.
5. Look for the most recent cache folder, and then open it.
6. Take note of how many configuration files are in this folder.  For example, looking in this folder for one of my WFEs, I see 1736, including the cache.ini.
7. Delete all files in this folder EXCEPT cache.ini.
8. Open the cache.ini file in a text editor, and then randomly modify the number, but keep it at the same number of digits.
9. Save the cache.ini file.
10. Start the SharePoint Timer Service.
11. Now watch the configuration folder.  It will start filling up with new configuration cache files quickly.  When it reaches the number you noted down in step 6, and you no longer see any new files being created, proceed to the next step.
12. Open a command prompt as Administrator.
13. Run the following command: Psconfig.exe -cmd upgrade -inplace b2b -wait -force
14. Check the Upgrade Status.

Notes

• Upgrade Status page: CA > Upgrade and Migration > Upgrade and Patch Management > Check upgrade status.
• Cache folder: You may get a Folder not found error trying to navigate to this folder.  If so, try navigating first to one of the higher tier folders, then double-clicking on each subfolder in turn.
• The path to psconfig is here: c:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\BIN\.
• I’ve also had this kind of problem when it seemed stuck on “10%”.  I had executed this command: PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures.  No issues until it reached Step 5 of 6.  Checking the upgrade log found no issues; there was an upgrade error log generated, but the errors logged were the pesky “web application is configured with claims authentication mode however the content database you are trying to…” warnings that I ignore.  I followed the procedure above, and I was able to successfully complete the upgrade.
• Re blog from http://alstechtips.blogspot.ca/2014/05/sharepoint-2013-product-configuration.html