Polylang crashes my site


I am having many problems with Polylang, for some reason the website crashes every time I add a 2nd language or add some CSS on the customizer for example.
I am using the child theme, and I work on a local environment with MAMP. The only way of getting it back to work is by cleaning the database.

Here is the log I get from WP_DEBUG if it helps

Fatal error: Uncaught Error: Call to undefined function add_settings_error() in /Applications/MAMP/htdocs/FootballXP/wp-content/plugins/polylang/admin/admin-static-pages.php:149 Stack trace: #0 /Applications/MAMP/htdocs/FootballXP/wp-includes/class-wp-hook.php(288): PLL_Admin_Static_Pages->update_page_on_front(‘23’, ‘23’) #1 /Applications/MAMP/htdocs/FootballXP/wp-includes/plugin.php(203): WP_Hook->apply_filters(23, Array) #2 /Applications/MAMP/htdocs/FootballXP/wp-includes/option.php(312): apply_filters(‘pre_update_opti…’, 23, ‘23’, ‘page_on_front’) #3 /Applications/MAMP/htdocs/FootballXP/wp-content/themes/jupiterx/lib/api/customizer/classes/class-multilingual.php(260): update_option(‘page_on_front’, 23) #4 /Applications/MAMP/htdocs/FootballXP/wp-includes/class-wp-hook.php(286): JupiterX\Customizer\Multilingual\CustomizerMultilingual::load_settings(’’) #5 /Applications/MAMP/htdocs/FootballXP/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #6 /Applications/MAMP/htdocs/FootballXP/wp-includes/plugi in /Applications/MAMP/htdocs/FootballXP/wp-content/plugins/polylang/admin/admin-static-pages.php on line 149

Thank you!
Best regards,


It seems like the function add_settings_error is missing which is being called by the plugin.

Have you installed the plugin completely? Can you try to re-install the plugin?

Are you using any cache plugin?


Thanks for your answer.
No, I’m not using any cache plugin, and I’ve installed it through the ‘add plugin’ section from WordPress, so I guess it is installed completely.
Now I tried deleting Polylang, cleaning the folder “languages” from wp-content, flushing the cache and re-installing it by uploading the zip file, and the issue is still the same…
When I found this problem the first time I thought it was because I previously tried another plugin, but then I decided to do a fresh install of wordpress and the theme to test it, and the issue was the same.


Okay, I understand.

Which cache are you talking about? Plugin cache?


The cache flush that you have on the theme settings. (on the Jupiter X tab)
I tried yesterday on a live site from a fresh install and seems to work, but I had very little time to test and didn’t use the child theme. Do you have any idea why not on localhost? Since I would prefer to work local.


Ok, after some more testing, I saw that it also crashes the live site… for English and Spanish seemed to work well, but the moment I added Chinese for example, the problem started again. I’m able to access the site, but not the wp-admin, which shows error 500 and my only solution so far has been to clean the database by searching and removing the zh_cn


This is very strange and needs more investigation.
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