It is hard to say what version of Qualtrics this is a problem in, but I am going with version 1923062 since that was the best I could find in the source code.
Anyway, I found that contact list authentication seems to work on the first distribution for an anonymous link survey, but if you need to stop the survey and delete the data to test it again, then you start to have problems with contacts not being able to login once the survey is brought back online again (especially if the contact started the survey during the first distribution).
The work around seems to be making a copy of the contact list you are authenticating against if you reset the survey data and redistribute the survey and set the authentication element in the survey flow to the new contact list. You should just be able export the contact list from Qualtrics (but make sure the ‘RecipientID’ data is not in the contact list when you import back into Qualtrics since you want new ‘RecipientID’s for the contacts).
‘Retaking a suvey’ is a problem with personal link distributions in the same way. Once you start a distribution and then delete data and try to retake the suvey…you have problems.
– June 16, 2016