Problems vendor registration

After installation, the vendor registration not work, have error: Failed to load resource: the server responded with a status of 404 (Not Found) /wp-admin/admin-ajax.php:1
I have installed theme and plugin compatible, but the result its the same.
And the vendor registration ist not correct because after the registration, the vendor has insert not like a vendor but like a Subscriptor client.
Please help me to solve this problems

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