If your customer has previously been able to login to their account, but can't now, it is likely they are entering either their email address or password incorrectly. (If you have recently started using Gingr, scroll down.)
Verify Email Address:
Go to the their Owner Profile anywhere in the app and find the email address they have on file. Verify with them that that is the email address they are attempting to login with and that they are spelling it correctly.
If they are using the correct email address to login, it is possible they are using the wrong password. They can reset their password from the customer login page. After clicking the Forgot Password? button, they will enter their email address and be sent an email to complete the password reset process.
Remember to save your changes. Once your customer has an email address on file, they may complete their Gingr registration process by going to http://your_business.gingrapp.com/customer and clicking on the blue 'current customer' button. (You may also have a customer portal link on your own website.)
Your customer will enter their email address and be sent an email directing them to complete their registration by creating a password. Upon creating their password, they will be immediately logged in to their account.