Problems accessing site

I’m hosting a site (among many others) that’s using the free version of the Polylang plugin.

Last week we started having problems accessing the site if we type type https://scr-smv.dk in the browser. If we try to access https://scr-smv.dk/da or https://scr-smv.dk/en the site works just fine.

When accessing https://scr-smv.dk we get this warning in the php error log:

[30-May-2023 06:45:45 UTC] PHP Warning: Trying to access array offset on value of type null in /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/include/language.php on line 300
[30-May-2023 06:45:45 UTC] PHP Stack trace:
[30-May-2023 06:45:45 UTC] PHP 1. {main}() /var/www/multi/scrsmv/htdocs/index.php:0
[30-May-2023 06:45:45 UTC] PHP 2. require() /var/www/multi/scrsmv/htdocs/index.php:17
[30-May-2023 06:45:45 UTC] PHP 3. require_once() /var/www/multi/scrsmv/htdocs/wp-blog-header.php:13
[30-May-2023 06:45:45 UTC] PHP 4. require_once() /var/www/multi/scrsmv/htdocs/wp-load.php:50
[30-May-2023 06:45:45 UTC] PHP 5. require_once() /var/www/multi/scrsmv/htdocs/wp-config.php:78
[30-May-2023 06:45:45 UTC] PHP 6. do_action($hook_name = 'plugins_loaded') /var/www/multi/scrsmv/htdocs/wp-settings.php:486
[30-May-2023 06:45:45 UTC] PHP 7. WP_Hook->do_action($args = [0 => '']) /var/www/multi/scrsmv/htdocs/wp-includes/plugin.php:517
[30-May-2023 06:45:45 UTC] PHP 8. WP_Hook->apply_filters($value = '', $args = [0 => '']) /var/www/multi/scrsmv/htdocs/wp-includes/class-wp-hook.php:332
[30-May-2023 06:45:45 UTC] PHP 9. Polylang->init('') /var/www/multi/scrsmv/htdocs/wp-includes/class-wp-hook.php:308
[30-May-2023 06:45:45 UTC] PHP 10. PLL_Frontend->init() /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/include/class-polylang.php:263
[30-May-2023 06:45:45 UTC] PHP 11. PLL_Choose_Lang_Url->init() /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/frontend/frontend.php:114
[30-May-2023 06:45:45 UTC] PHP 12. PLL_Choose_Lang_Url->set_language_from_url() /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/frontend/choose-lang-url.php:34
[30-May-2023 06:45:45 UTC] PHP 13. PLL_Choose_Lang->home_language() /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/frontend/choose-lang-url.php:58
[30-May-2023 06:45:45 UTC] PHP 14. PLL_Choose_Lang->get_preferred_language() /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/frontend/choose-lang.php:208
[30-May-2023 06:45:45 UTC] PHP 15. PLL_Model->get_language($value = FALSE) /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/frontend/choose-lang.php:193
[30-May-2023 06:45:45 UTC] PHP 16. PLL_Model->get_languages_list($args = uninitialized) /var/www/multi/scrsmv/htdocs/wp-content/plugins/polylang/include/model.php:282
[30-May-2023 06:45:45 UTC] PHP 17. array_map($callback = [0 => class PLL_Language_Factory { private $options = […] }, 1 => 'get'], $array = [0 => ['name' => 'Dansk', 'slug' => 'da', 'term_group' => 1, 'term_id' => 3, 'locale' => 'da_DK', 'is_rtl' => 0,
'w3c' => 'da-DK', 'facebook' => 'da_DK', 'home_url' => 'https://scr-smv.dk/da/', 'search_url' => 'https://scr-smv.dk/da/', 'host' => NULL, 'page_on_front' => 476, 'page_for_posts' => 0, 'flag_code' => 'dk', 'flag_url' => 'https://scr-smv.dk/wp-content/plug
ins/polylang/flags/dk.png', 'flag' => '', 'custom_flag_url' => '', 'custom_flag' => '', 'active' => TRUE, 'fallbac
ks' => […], 'is_default' => TRUE, 'term_props' => […]], 1 => ['name' => 'English', 'slug' => 'en', 'term_group' => 2, 'term_id' => 5, 'locale' => 'en_GB', 'is_rtl' => 0, 'w3c' => 'en-GB', 'facebook' => 'en_GB', 'home_url' => 'https://scr-smv.dk/en/', '
search_url' => 'https://scr-smv.dk/en/', 'host' => NULL, 'page_on_front' => 511, 'page_for_posts' => 0, 'flag_code' => 'gb', 'flag_url' => 'https://scr-smv.dk/wp-content/plugins/polylang/flags/gb.png', 'flag' => '

Does anybody know what to do about the problem?

If we disable the Polylang plugin, https://scr-smv.dk can be accessed without any problems.

The site and all the plugins are all fully updated.

The page I need help with: [log in to see the link]