The Module Create fail when using WHMCS MU Provisioning to create multisite blog

I have requested support from WHMCS on this matter also, but I have a feeling this error is a plugin error since WHMCS does not include this function.

I use WHMCS MU Provisioning for automated creation of multisite blogs. This worked fine with previous install of WHMCS (5.2.16). After upgrading to WHMCS 5.3.5 , there is no communication between WHMCS and the WP MU site, as shown in the extract from activity log:

Module Create Failed - Service ID: 30 - Error: ERROR: The password you entered for the username admin is incorrect. Lost your password?:
- 12/03/2014 15:33 - Client - 85.167.157.1
Running Module Create on Order
- 12/03/2014 15:33 - Client - 85.167.157.1
Email Sent to test twenty (Order Confirmation) - User ID: 30
- 12/03/2014 15:33 - System - 85.167.157.1
New Order Placed - Order ID: 31 - User ID: 30
- 12/03/2014 15:33 - System - 85.167.157.1
Email Sent to test twenty (Welcome) - User ID: 30
- 12/03/2014 15:33 - System - 85.167.157.1
Created Client test twenty - User ID: 30
- 12/03/2014 15:33 - System - 85.167.157.1

When checking Service ID: 30 - Client Profile the Login to Wordpress link (mared in red) shows:
http://101hobbies.com/wp-login.php?log=testhobb&pwd=294&Kjums

The log=testhobb in the link above is the client username. I expected this to be the Wordpress Admin username. Password is the correct WP admin password.

I've checked the WP server setup and login to the WP MU site from server setup screen is OK.