In the admin panel, open the Design : SEO URL section and filter the entries by the filter "Route" = "common/home".
All such entries in the Keyword field should be empty, as in the screenshot below:
If you have something written there, for example a slash "/" or a language code, you need to edit and clear the Keyword field.
Attention! The system does not allow you to create an empty SEO URL.
To solve this problem, you need to install the fix allow_empty_seo_url.ocmod.zip or edit the SEO URL through the database in the "oc_seo_url" table.
In order for the system to allow adding empty SEO URLs, the option "Same SEO URLs" must be enabled in the module settings.
If you do not have records for all languages, you need to create an SEO URL record for each language, where query = "common/home" and keyword is empty value (as in the screenshot above).
After any manipulation of the SEO URL, you need to clear the system cache in order to update the cache of the SEO PRO. The SEO PRO cache is automatically reset when you save the settings of the "Multilang SEO Pro" module, so you can simply re-save the module settings.