If you are getting this error, the (finance/design tool) login for the sales rep is not defined. Configure it in the Sales Rep's integration settings.
The email in the integrations setting must match exactly what is in design tool or financier's system.
If you are a sales rep, update your email by following these steps. Click your name in the top right > Edit My Profile > and then V2 User Profile in the top right of your profile. Once on the V2 profile, click the integrations tab on your account settings, scroll down to the appropriate setting and then fill in the correct email address.
If you are a company admin, update a user's email for them by clicking Settings > Org > Users and then searching for the user you need to edit. Click the user's name and then once inside their account settings, click over to the integrations tab. Scroll down to the appropriate setting and enter the correct email address.