CSVI : 500 Internal Server Error

The Internal Server Error is probably the worst error you can get. The error means that the server is telling you something went wrong but not what has gone wrong. It is now up to you to find out what has gone wrong.

Kown causes
There are a number of known causes and easy fixes:

Folder and or files do not have the correct priviliges
Solution: Set the correct priviliges for the folders and files
Folders should have permission 755
Files should have permission 644
Missing folders and or files
Solution: Re-install necessary packages and/or patches
Trying to resize images that are too large
Solution:
Make sure your large images are not too large
Create your own thumbnails
Set the maximum size of the large image CSVI should create a thumbnail for (CSVI Pro)
Old PHP version
Solution: Check that the PHP version used is at least 5.4 but recommended is PHP 5.6 or higher
BOM in your file
Solution: Set the Auto-detect delimiters to No in your template and specify them manually in the template.
Export of SEF URLs
Solution: When exporting SEF URLs it can be a huge strain on the server. Instead of generating SEF URLs during export you can pre-fetch the SEF URLs by going to Maintenance -> Select your extesion -> Refresh SEF URLs. This will populate the database with the generated SEF URLs and the export will read them from the database instead of requesting them from the server. Make sure you have set the Domain name in the CSVI Settings.
Error reporting
In some cases the 500 Internal Server Error can be changed to a visible error by setting the Error Reporting to Development as explained in the steps below.

Go to System -> Global Configuration
Click on the Server tab
Set Error Reporting to Development
Error Reporting
Click on Save & Close
Once the Error Reporting is set to Development, run the import again and see if you get the real error. If not, you will have to check the Server error log section.

Server error log
The real error is in the server error log. This may not be a log you have access to, so contacting the hosting provider is advised in that case. Explain to them the situation and that you would like to know which error has been generated by the server. With the real error in hand it should be easy to fix the issue. If you need help, post the real error in the forum and we will gladly assist you.