There isn't really enough information here to give a full answer, but 'Bad Request Unable to verify your data submission' means that Craft is not getting supplied the correct CSRF token.
To confirm, try turning off CSRF protection in your config:
I finally ended up with this SQL query, which result to disable all Entries of a site version:
UPDATE `craft_elements_sites` SET `enabled` = '0' WHERE `craft_elements_sites`.`siteId` = 2;
Where 2 is the siteId. After that, don't forget to clear the templates caches.
If you're on Craft 3.5+, you can use the cpHeadTags config settings to achieve this.
'cpHeadTags' => [
// Traditional favicon
['link', ['rel' => 'icon', 'href' => '/icons/favicon.ico']],
// Scalable favicon for browsers that support them
['link', ['rel' => 'icon', 'type' => 'image/svg+xml', 'sizes' => 'any', 'href' => '/...