If your coupon page link doesn't lead to the actual coupon page but rather goes to the Coupon Reach login or to an error page, possibly your coupon page's name/title has any of these characters: "/" (forward slash) and "%" (percent symbol)

These characters/symbols can disrupt the whole coupon link so it won't pull out the page properly.

Another possible cause would be an unfinished setup or a mistake when setting up the CNAME Domain for your Contact Reach account. Please check out this article: https://support.mylocalagency.co/a/solutions/articles/44002295244