The error message you're encountering, "TemplateSyntaxError at /payment/3490/ Invalid block tag on line 369: 'endif'. Did you forget to register or load this tag?" suggests that there's a problem with the template syntax in your Django application, specifically with the use of the {% endif %} tag. Here's a checklist to resolve the issue: Mismatched Tags: Ensure that every {% if %} tag in your template has a corresponding {% endif %}. It's a common mistake to have more endif tags than if tags or vice versa. Tag Registration: Make sure that all custom template tags you might be using are properly registered with Django. If endif is supposed to be a custom tag, then it should be defined in a templatetags directory within one of your apps and loaded using {% load %}. Correct Syntax: Double-check the syntax for the Django template. It should be {% endif %} without any additional characters or typos. File Corruption: Sometimes, template files might become corrupted or have invisible characters that cause syntax errors. Opening the file in a different editor or viewing hidden characters might help identify the issue. Django Version: If you have recently upgraded your Django version, ensure that all your templates are compatible with the new version. Sometimes, new versions deprecate certain syntax. To fix the problem, go through the template file and make sure that all control structures are properly opened and closed, and that you have not misspelled any of the template tags. You can also look above and below the indicated lines to find any unclosed tags. If endif is a custom tag, make sure it's properly registered and loaded in your template. If you're not using any custom tags, it's likely a mismatch issue with the standard if and endif tags.