So.. you have succesfully updated Magento, and now you are facing this cursed Error 500. This is a fairly common error of Magento , and I’ve gained a lot of experience facing it. Let’s see how to solve it.
1 – Error 500
Try to remove (after you have copied the file elsewhere) the .htaccess file of the main dir and see if the website load. Yes? Perfect, at least we know what we have to resolve. Don’t upload the file untile the third point.
The fact the error is in the .htaccess file is a good sign, because it mean that we have found the cornerstone of the error. If you remove the file and nothing happens, I don’t know how to help you.
Sometimes the errors 500 and 503 going out all together when trying to update Magento, and solving a problem just make another thing to pop out.
Sure enough, when you remove the .htaccess is very probably that an Error 503 will pop out, and here we arrive to the second point.
2 – Error 503
This is pretty simple, fortunately. Try to remove the maintenance.bak file from the home directory of the website. Surely this will solve the problem. The maintenance.flag.bak file can be left on the directory, it does nothing harmful.
This is an error that the Magento team could annotate better.
In few words, when you update Magento, the CMS put himself in a maintenance mode (and that is good), but after the update is finished, it can’t restore autonomously to the working status. Very clever.
You have resolved the error 500, even the 503, now let’s try to resolve this.
This is a more subdole problem, but none less resolvable. We are still on the .htaccess.
In the .htaccess files of the folders:
Find the line where it’s written +FollowSymLinks and replace it with +SymLinksIfOwnerMatch
Now try to upload the file .htaccess that you have removed (like I said in the first parte of the article).
If it still not working, find the error LOG of the server and try to study them.
Par example, i once had an error inside the .htaccess file inside the media/ folder, and I have to comment the first line like this: #Options All -Indexes to make it work.
If your problem is not one of one listed before, search the log for the real cause and try contacting your hosting.
This passages have saved my life 2 different times, when I’ve updated Magento from 1.4 to 1.8 and when I updated Magento again from 1.8 to 1.8.1
My advice is update Magento only if you really need, because as you can see Magento is a very pain when it comes to update.