The Email field can contain only one email address, remove multiple email addresses for contacts
If you want to change familyname, firstname or email of an existing contact, you must specify the yve_id or customer_number, otherwise yve will create a new contact with the new data
Remove leading or trailing spaces, all characters of a cell are evaluated as input (ie also behind emails or predefined values)
Your .xlsx file should contain only one workbook with your list. Remove all data that should not be considered as input
For participants you need i.d.R. Only familyname, firstname, email, and gender - all other fields are optional
Use the CRM fields (source, salescontact, ...) to assign participants to specific sales activities
Use the freely definable fields (reg_info1, ...) for further information