Fix Theme/Plugin Crash

Sometimes theme/plugin installation and updates might crash the whole WordPres site due to issues with conflicts, incomplete updates and WordPress core. If you can't login to WordPress admin after a theme/plugin installation or update, follow this tutorial to fix it.

Can you access wp-admin?

First check if you can access wp-admin. If you can access wp-admin, then you can use the WordPress theme/plugin installer to restore the conflicting theme/plugins.
To reinstall the conflicting theme/plugins, you basically need to re-install the theme/plugin zip (it is the same procedure as installing a new theme/plugin - upload the theme/plugin zip and replace it).

To restore a theme crash

If the issue is a theme crash/conflict and you can't access wp-admin, you would need to connect to your server using a FTP software.
From the root folder where you installed WordPress, go to 'wp-content > themes' folder.
Rename the activated theme folder to something else. Example: if you see critical error message related to Themify Ultra theme, then you would rename 'themify-ultra' folder to something else such as 'themify-ultra-crash'. When the activated theme folder is renamed, WordPress will deactivate the theme.
Now check if you can login to wp-admin. If you can login to wp-admin, then go to "Appearance > Themes > Add new" and upload the theme zip to reinstall it (if you are using a Themify premium theme, you can download the latest theme ZIP version from the Member Area).
NOTES: After you rename the activated theme, but the errors remain and you can't access wp-admin, the issue might not be related to the theme. The issue could be the plugin(s) or WordPress core. Or your server might be caching the files on the FTP server (purge the server side cache or contact your host provider if you have server cache that you can not purge).
After you resintall the theme and the site is fine, you can delete the renamed theme folder on the FTP server (don't keep the unused theme folder on the server).

To restore a plugin crash

If the issue is related to a plugin (eg. you see critical error messages related to a certain plugin) and you can't access to wp-admin, you would need to connect to your server using a FTP software.
From the root folder where you installed WordPress, go to 'wp-content > plugins' folder.
Rename the conflicting plugin folder to something else. Example: if the issue is the Themify Builder plugin, then you would rename the 'themify-builder' folder to 'themify-builder-crash'. WordPress should deactivate the plugin once its folder has been renamed.
Now check if you can login to wp-admin. If you can login to wp-admin, then go to "Plugins > Add new" and then reinstall the pluign using the latest plugin zip.

Not sure what is crashing the site?

If you are not sure what is crashing the site, try the following steps:
- Connect to your server using a FTP software. Go to "wp-content > themes" folder, rename the current activated theme folder to something else and check wp-admin. If you can access wp-admin after renaming the activated theme folder, then reinstall the theme.
- After renaming the theme folder and still can't access wp-admin, then revert the theme folder rename. Go to "wp-content" folder, then rename the "plugins" folder to something else. This should deactivate all plugins. Then try to access wp-admin. If you login to wp-admin, then go to Plugins admin page and activate the plugins one by one to find which one is crashing the site. After you find the conflicting plugin, you just need to reinstall that plugin and re-activate the plugins you had before.
- After renaming the activated theme folder and plugins folder, but still can't wp-admin, then the issue could be WordPress core. Try to reinstall WordPress core: download it from wordpress.org, extract the WordPress zip, replace all files and sub-folders except the "wp-content" folder on your FTP server (the "wp-content" folder is where it stores the themes, plugins, and your uploaded content).
After you've tried all steps above and still can't access your site or wp-admin, the issue might be server related issues. Contact your host provider for assistance.