Why are we seeing a 500 Internal Server Error when previewing all answers?
Answer Preview / Customer Portal
This is generally caused by invalid customized code in the answer_quick_preview.php file. To resolve this, it's recommended to remove invalid code and/or reset this file back to default. This file can be modified via Customer Portal.
The path to this file is: development/views/admin/answer_quick_preview.php. Once modified, deploy changes to correct the error in your production site.
Customer Portal pages within the Development directory can all be replaced with the corresponding OOTB (out of the box) file within the RightNow directory. As all folders within the RightNow directory are read-only, these out-of-the-box default pages will always serve as core backups for setting your customized pages back to a non-customized state within the Development folder.
For more information and steps, refer to Answer ID 4058: Resetting Customer Portal to default pages.