I set the site in multilanguage like this: website.com/it website.com/es but when I access website.com it redirects for the default language which is English to website.com/en and returns a 404 error, but website.com is the language English default, other URLs also return 404 error website.com/it, how can I resolve it?

Send url please.
Try to resave your oermalink settings and regenerate htaccess.

home page redirect on website.com/en and have issue 404, in general settings I enabled language code, pls see screen. My .htacces is this

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

Eveything looks correctly.
Have you resaved permalinks settings?

yes not work same errore 404 in all language url redirect website.com/en for english, but english is default website.com and for spain website.com/es but have 404 error i

require multisite plugin?

i want create subdomain for multilanguage like this website.com/it website.com/es etc with new osclass installation, require new api key for all? multilanguage option in admin not work, this solution is better, I would like to show the ads not all mixed of all the locations in home and in the search, example for website.com/es show only ads in Spain website.com English default

No plugin is required.
Multisite can sync multiple websites (user base).

can you help me please? url redirect not work and language default redirect to website.com/en instead it should be website.com why there is an error 404?

Please PM ocadmin & ftp login, will have a look