If fulfiller users are logged in and click on notification survey link As per sequence all steps are displaying and complete the survey successfully.

If fulfiller users are logged off (i.e., as a GUEST) and click on notification survey link (Opens in a different browser as a new session). The error message appears as  "You have completed this survey".

London Patch 10

Custom email notification script for surveys and the script contained the below URL:

https://<instance-name>/assessment_take2.do?sysparm_assessable_sysid=(sysidnumber)&sysparm_assessable_type=e35fac98dbdf67407217f4eb0c9619b0&sysparm_reader_view=true

The same link leads to the survey and the customer completes the survey and then they use the same link for the survey response, therefore, the error message appears because the link is expired/taken.

This is the OOB link for guests as an example:

https://<instance-name>/nav_to.do?uri=assessment_take2.do%3Fsysparm_assessable_type=87186844d7211100158ba6859e610378. 

You will not be able to access this link, but if you take a closer look at this it does not include "sysparm_assessable_type record".

You will have to modify the URL for guests to solve the issue.