If the email link in an email button set up through the Email Editor sends the guest to a 404 page, take a look at the link in the button. If in the Email Editor you see https://www.testlink.com but when you right-click on the button in the email and the link shows something like http://email.testlink.com/ls/click?upn=[long string of alphanumeric characters], then this is because of Click Tracking (a setting enabled in SendGrid).
To disable Click Tracking, you will need access to SendGrid. If you do not have access to SendGrid, please submit a ticket to Punchh Support.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)