Problem:
I'm using a toolset user cred form on a multisite installation of WordPress. If users only have an account on one subsite, the registration works. However, if users are registered on one subsite, they aren't currently able to register on a subsite. Instead, they get an 'that email already exists' and 'that username already exists' error and an administrator has to give them access to the subsite. I would like to give users the ability to register for each site, without requiring approval from an administrator.
Solution:
Toolset register user form is for creating new users, you can not create two users with the same email address, so you will get those error message:
'that email already exists' and 'that username already exists'
You might consider custom codes, for example:
https://toolset.com/forums/topic/separate-user-registration-on-multisite-network/#post-1557013
Relevant Documentation:
