[Closed] I get a 404 error with I try to log into wp-admin

hello again,

I thought I had fixed my problem but it "came back".

I disabled sitepress-multilingual-cms plugin and could get back into the back end of my WP.

By the way, I have checked and the Settings Language were still in Spanish and my wp-config.php mentions ES too:
define( 'WPLANG', 'es_ES' );

If I enable sitepress-multilingual-cms plugin again, I lose access to the back end because visiting /wp-admin redirects me to hidden link
and shows a 404 error page

BTW, this is my .htaccess in case it's helpful information:

#Begin Really Simple Security
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{HTTPS} !=on [NC]
RewriteRule ^(.*)$ hidden link{HTTP_HOST}/$1 [R=301,L]
</IfModule>

Options -Indexes
#End Really Simple Security
# BEGIN WordPress
# Las directivas (líneas) entre «BEGIN WordPress» y «END WordPress» son
# generadas dinámicamente y solo deberían ser modificadas mediante
# filtros de WordPress.
# Cualquier cambio en las directivas que hay entre esos marcadores
# serán sobrescritas.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

#Redirect 301 /es/wp-login hidden link

# END WordPress

# BEGIN DS-XML-RPC-API
# Las directivas (líneas) entre «BEGIN DS-XML-RPC-API» y «END DS-XML-RPC-API» son
# generadas dinámicamente y solo deberían ser modificadas mediante filtros de WordPress.
# Cualquier cambio en las directivas que hay entre esos marcadores serán sobrescritas.

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^hidden link [NC]
RewriteCond %{HTTP_REFERER} !^http(s)?://(www\.)?google.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ – [NC,F,L]

<Files xmlrpc.php>
order deny,allow
deny from all

Allow from 122.248.245.244/32
Allow from 54.217.201.243/32
Allow from 54.232.116.4/32
Allow from 192.0.80.0/20
Allow from 192.0.96.0/20
Allow from 192.0.112.0/20
Allow from 195.234.108.0/22
Allow from 192.0.96.202/32
Allow from 192.0.98.138/32
Allow from 192.0.102.71/32
Allow from 192.0.102.95/32
</Files>

# END DS-XML-RPC-API