When activating an organization account with a new username, the password field does not accept special characters and the error message does not specify if special characters are allowed.
The ArcGIS Online default password requires letters and numbers for password. The password policy for the organization can be changed to include special characters after activating the organization and administrator usernames. Refer to <a href="https://doc.arcgis.com/en/arcgis-online/administer/configure-security.htm" target="_blank">https://doc.arcgis.com/en/arcgis-online/administer/configure-security.htm</a> for information on how to configure security settings in ArcGIS Online to be able to update the password to include special characters.