Status 400 on admin-ajax.php

Hello, I’v installed the plugin, and when I search a product to add it to the frequently bought together, I am getting this error in the console:

Failed to load resource: the server responded with a status of 400 ()

On file:
[path]/wp-admin/admin-ajax.php?_fs_blog_admin=true.

It is on a staging site, but I don’t think that is the issue.

Thanks,

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