Dynamic DNS DNS-O-Matic Service Authentication Error

[kp74508]

When using the DNS-O-Matic Service type as the following entry I receive the error, "php-cgi[84913]/services_dyndns_edit.php: Dynamic DNS: (Error) Authentication failed"

Service type: DNS-O-Matic
Interface to monitor   : WAN
Hostname   : all.dnsomatic.com

However, using the Custom Service type as the following entry with the same credentials (email address) updates successfully.

Service type: Custom
 Interface to monitor: WAN
 Interface to send update from: WAN
 Hostname   : all.dnsomatic.com
 Update URL:updates.dnsomatic.com

Am I missing something here?