No one likes this one. You enabled a new theme on your WordPress multi-site site and you got the instant screen of death.
If you try all the other methods first and have no luck, then try this next.
If you can’t change the theme in admin, or find yourself locked out then we can try and update the theme used in the database directly.
Note: I am not responsible for any problems created by following any of this advice, I recommend you do your research and understand what you are doing before modifying your database.
Open phpMyAdmin from WPMU
First go into phpMyAdmin in WPMU, it’s in Hosting / Tools / Manage database
Now locate the wp_iz_X_options table, where X is the id of your multisite (the iz may also be different). If this is your primary site then it will be wp_iz_options (no number).
You can find the site ID in WordPress main multisite admin (hopefully you have access to that!) – go to Network Admin / Sites / Then Edit Site on the site you are having issues with, check the URL, it says id=X at the end, this is your ID.
Change the number of rows to 50
Scroll down and look for stylesheet and template entries:
Edit these and put in a theme name that is enabled and working in your site.
How do I know what themes are enabled on my WordPress multisite network?
Good question! It’s hidden away in the wp_xx_sitemeta table, called [allowedthemes]. Find the table in phpMyAdmin and open it up, then search for ‘theme’ by typing it in the ‘Filter rows box’.
Here it is:
Is it working now?
Okay you can try a refresh once this is saved but you might find it still shows the error, in which case try this:
No, then clear the Object Cache in WPMU hub
This is in Hosting / Tools:
Click clear and try your site again, hopefully it’s back to normal!