User Sync is not working: Connection Error

Hello, I am having a problem using User Sync. When I try to enter the details and click Sync, I receive the following:

There was a connection problem. Please check the URL and Key of the Master site.

As far as I can tell, everything is correct, it just won’t connect.

THIS IS NOT A MULTISITE!!! No multisite is installed ,these are two separate installs.

Any help here would be great,

Log file below:

Log file:

[2013-08-15 02:43:39] 01 – new subsite conection – central_url=http://community.tianjinbang.com;; replace_user=1;; overwrite_user=1;;***

[2013-08-15 02:43:39] 02 – sending request – url=http://community.tianjinbang.com/wp-admin/admin-ajax.php?action=user_sync_api;;***

[2013-08-15 02:43:39] 04 – sending request: something went wrong***

[2013-08-15 02:43:40] 0-10 – ajax actions***

[2013-08-15 02:43:40] 4-10 – hash sum error***

[2013-08-15 02:43:40] 3-10 – p or hash not set***

[2013-08-15 02:46:01] 01 – new subsite conection – central_url=http://community.tianjinbang.com;; replace_user=0;; overwrite_user=0;;***

[2013-08-15 02:46:01] 02 – sending request – url=http://community.tianjinbang.com/wp-admin/admin-ajax.php?action=user_sync_api;;***

[2013-08-15 02:46:01] 04 – sending request: something went wrong***

[2013-08-15 02:46:01] 0-10 – ajax actions***

[2013-08-15 02:46:01] 4-10 – hash sum error***

[2013-08-15 02:46:01] 3-10 – p or hash not set***

Print Screens of my configuration, to show there are no mistakes in the setup.

https://s3-ap-southeast-1.amazonaws.com/tianjinbang/WPMU/Master+Site.jpg

https://s3-ap-southeast-1.amazonaws.com/tianjinbang/WPMU/Sub+Site+(Before+Error).jpg

https://s3-ap-southeast-1.amazonaws.com/tianjinbang/WPMU/Sub+Site+(Error).jpg

Additional Information

Both wordpress installs are located on separate servers.

I am using the latest wordpress / buddypress installs. (Also the latest User Sync).

Server 1 is hosting just a regular WordPress install

Server 2 is using wordpress + buddypress.

Again: NO MULTISITE! :wink:

Many thanks in advance for your help.