GTM https health monitor Not, but tcp YES

Hi,

I've got a GTM that round robin between two LTMs.

On the LTMs we've got a Virtual Server using https [port 443].

From the GTM if I monitor the pools [whose members are the VS on the LTM]:

- using health monitor 'https' -> it shows the red diamond
- using health monitor 'tcp'   -> it shows and hold the green circle

The GTM are not using any certificate, the LTMs for the VS mentioned above are using signed certificates.

Why the https monitor is not showing green on the GTMs? As the VS allows https request.

Thanks.