Solman 7.1 - Ping called unsuccessfully

Hello experts,

We're currently implementing the Technical Monitoring in our landscape and we're getting the following alert on some AS-ABAP instances:

[RC=600] URL http://<fqdn>:8<sn>0/sap/public/ping called unsuccessfully.

Telnet works just fine from the Solman to the target instances and the called service is active on SICF.

In fact, I even tried calling the link directly from an IE browser and I get a successful response from the call.

Would you guys have any other idea related to this?

Thanks,

Ricardo