@Erica Gittens15 The error you've shared happens in two cases:
- The user kept a window open for a long time and then submitted the registration form. For security reasons we use CSRF tokens on all our forms that expire after an hour.
- The browser that they're using is very old. By very old I mean IE 10 or IE 11 which are not supported by Microsoft anymore and has less than 1% market share.
Currently, invitations expire after 1 month and the error message states that the invitation is expired or has been used before.