Please make sure you are adding the correct record as changes of CNAME record might need at least 4 hours of propagation period.
You could like to add record as below where will point docs.domain.com as CNAME to ghs.google.com.
docs IN CNAME ghs.google.com.
1. Login to your Website Panel via http://cp.domain.com.
2. Seek for your domain.
3. Select on Edit DNS zone records.
4. Select "Add Record" for new creation or click on the pencil icon for the old record that need to change for modification.
5. Please use the format as below.
Record Type: CNAME
Record Name: docs
Record Data: ghs.google.com
6. Click on Save.