Why can't I enable the auto approve seller option?

Normally setting it to "Yes" should do this, but if it doesn't work it can be related to some other settings, like those from "Seller Verification Settings". 

For example, when we implemented this, it didn't make sense for us to auto-approve sellers when they are required to upload a CV, because we thought that the admin may want to check the CV manually before doing so.

Please submit a support ticket if you require additional help.