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Why didn't the participant receive the survey I sent?

If a study makes use of the Surveys (ePRO) feature and surveys are not sent as expected, there are several things you can check in the study. Find out how to troubleshoot issues with the delivery of surveys below.

Review the status

You can find an overview of survey invitations in the 'Surveys' tab of the relevant record or in the general 'Surveys' tab, these overviews contain a 'Status' column which should display the invitation's status. This status label provides a simple reference to quickly tell whether the survey has been sent successfully or not. In Castor, survey invitations are assigned one of eight different status labels. When checking if a survey invitation was sent, the status of the invitation can provide some insight:

Sent: The survey invitation has been sent, but was not yet opened by the respondent.

Failed - this status will be shown in studies on the US server, if the email address is incorrect or empty. For other servers (i.e., EU, UK, AU), this status will only be shown if the email address field is empty and if the automation engine is used to send surveys.

Note: Currently, for EU, UK, AU servers, it is not possible to identify a survey invitation that was not sent to the recipient properly (most likely because the email address is incorrect). The status will be shown as 'Sent'. If you suspect that this could be the case for you, we recommend double checking the email address with the receiver. After confirming the email address with the receiver, you can contact Castor support so we can confirm its status for you.


If the invitation's status label is 'Sent' but a participant did not receive the survey, it is advised to consider the following scenarios:

  • The email was sent to the recipient's spam folder. If a survey invitation email is found in the spam or junk folder, the recipient should move the email out of the spam folder and into their main inbox. In some cases, unmarking or moving this email to the primary inbox will indicate to the mail client that a participant would like to receive these emails in the future. 
  • The email is filtered by the security filter of the recipient's server and is in the quarantine area before it could be released into the recipient's inbox. Some institutions have very strict emailing policies, adding the address from which Castor surveys are sent ( as a safe email address should help resolve this.
  • An incorrect email address was entered. In this case, the first survey invitation sent to an incorrect email address will be shown as 'Sent'. When a survey participant has not filled in the survey on time, the survey invitation may be re-sent by a study user. Only when a survey is re-sent to the incorrect email address, the status will change to 'Failed' or a server error appears which indicates that the provided email address is not valid. 

Review schedule

If the surveys are sent using a schedule, it is recommended to check whether the schedule is set up correctly. In the case where several surveys should be sent in certain intervals starting from the present time/date, it is important to include 0 at the beginning of your schedule.

For example, if a survey needs to be sent on three occasions at an interval of two weeks, the schedule should be as follows: 0,14,28. The 0 in the beginning of the schedule indicates that the first survey should be sent today (now), again in two weeks and the last one in four weeks.

Below is an example of a correctly configured schedule:

This schedule can be applied when creating a survey invitation:

Once the schedule is applied, the survey invitations will be planned in the following way:

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  1. Castor Support Team

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