To creat a sub account for your staff or partner, you need to follow 4 steps.

1-create a role (Please always give dashboard permission to no matter what role it is, otherwise your staff may not be able to log in their account.)

2-create a sub account

3-assign the role to the sub account you created

4-assign your store to the sub account you created(Please assign at least one store to your staff account, otherwise they may not be able to log in their account.)

Here it is an example

Please always give dashboard permission to no matter what role it is, otherwise your staff may not be able to log in their account.