Expires on: 01 Mar 2019
Current date: 01 Jan 2018
Mismatch between domain name of you had attached to the site and inputed CNAME of DNS server.
For example, in the following figures, domain is registered example.com for Shifter, but www.example.com is assigned for Shifter's site on DNS.
When visitors access www.example.com, they'll get
Custom domain on Shifter
Remove current domain from Shifter then assign your domain name (e.g. www.example.com) to it.
Check out and follow Step 2: Add Domain of Assigning a custom domain name on Shifter.
If you want to use/assign both of example.com and www.example.com to Shifter, never forget input example.com to Domain Name and www.example.com to Alternative Names.
After that click [Submit] and verify your domain, then attach it.
You'll get assigned domains, like below figure.
After attaching domain.
DNS settings will be