Message server does not give application server list via HTTP

When I go to the URL http://<messageserver>:<msport>/msgserver/text/logon or .../msgserver/text/aslist there are no application servers listed (just the version number). However if I go to the message server monitor (transaction SMMS), I can see the application servers.

Other ms URL commands work, such as .../msgserver/text/lglist. However I need .../msgserver/text/logon to work because this is how SAP Web Dispatcher queries the message server to find out which application servers are available...

Any help greatly appreciated...

Best regards

Jane