This is another common problem that almost every WordPress website encounters at least once. There are several potential causes.
- Exhausted PHP memory limit
- Corrupted plugin functions
- Corrupted theme functions
- Corrupted .htaccess
Solution #1. Increase the memory limit
Follow the same steps to increase the memory limit as mentioned in the previous step.
Solution #2. Edit .htaccess file
Since the problem is usually caused by a corrupted .htaccess file, you would need to edit your .htaccess file. Open your .htaccess file from the FTP or file manager and rename it with .htaccess old. Refresh your website and see if the problem persists. If this fixes the problem, click on settings > permalinks and hit save changes to reset .htaccess.
Solution #3. Deactivate all the plugins
If changing your .htaccess file did not have any impact on the problem, you might want to check your plugins. Deactivate all your plugins by clicking on plugins ? installed plugins. Choose “deactivate” from the “bulk action” drop down and hit apply. It will automatically deactivate all your plugins. Now go to your website, refresh it and check if the error is gone. If so, activate your plugins one by one and see which plugin has caused the problem.
Solution #4. Replace wp-admin and wp-includes folders
If nothing worked, try replacing your wp-includes and wp-admin folders with fresh copies from a WordPress install. Save them and upload. Refresh the browser and see if the problem is resolved.