When adding a manual assignment in the Spots tab of the SignUp's Organizer view, you may see this warning message when you click "Add a New Participant":
The message means that the Participant is already listed on the SignUp's Participant roster or in your Contact List and you should instead select the person from the pull-down Participant list shown.
If the email address firstname.lastname@example.org is already on the Participant list, but you click Add a New Participant and try to add that email address and contact information manually, you will get the warning.
To assign the Spot, instead type the person's name into the search box and choose the Participant name from the pull-down menu list shown.
Participants Sharing Email Addresses
Adding assignments manually in the Spots tab of your Organizer view only supports recording one name per unique email address. If you have Participants/family members sharing an email address, one of these options will work:
1) You may give the second Participant an assignment by clicking "Add a New Participant" and then entering the person's name and phone number, but leaving the email address field blank. (With this method, the Participant will NOT get a confirmation or reminder message and you will need to alert them of their assignments).
2) If you selected the option allowing Participants to Sign Up Others (such as family members or team members) in the Details tab when setting up your SignUp, you may then access the SignUp from the SignUp's Shareable Invitation Link and assign another person using the shared email address. NOTE: Be sure to logout of SignUp before using the Shareable Invitation Link and logout again after saving the person's assignment. Please also see: How do I sign up someone else (a family member, or my team or group members)?
3) If the Participant has a Gmail account, you may add an assignment for another person using the "+name" feature to clone the email address. SignUp will then view each email address/Participant record as unique, but all notifications will be routed to the original email address.
For example, if Sammy@gmail.com is the original Participant's email address and you want to make assignments for Sammy's Spouse, Ella and Child, Jo, then you would add assignments for Sammy+Ella@gmail.com and Sammy+Jo@gmail.com and all notifications would go to the Sammy@gmail.com address.