User access - can not log in

User access - can not log in

Hello again,
 
I did follow the steps stated in a previous post in the form by having my staff creating their Zoho accounts, and I added their email address to share so they can add and view records ( the permissions which I choosed- add-view) but when the user logs in theough the my site which I Iframe it, the get the following message after they enter their user name and password. " You have logged in as kevin. You are not allowed to access this form. Please click here to login as a different user. Click here to go to your Home Page."
What should I do to have this user/s to access the form which they log in through my site to enter and view data?
 
Thank you,