ZCS 6.0.4 Insert signature problem in webmail

[mattoni]

Hello,

we have more ZCS servers, and I advert problem in webmail, Preferences > Mail > Signatures.

We have there icon for "Insert images" in html. On ZCS 6.0.4 it's doing nothing when I try to click on that icon. None error message.

Curiosity is on other ZCS server release 6.0.9, where we don't have actually Icon for "Inser images", there is just "Insert images via URL".

Other two are without licences, On 3rd ZCS server we have licence and there is signatura working ok. It's 7.1.3 version.

Can you please advice me to find right about Insert signature in webmail on ZCS. I need to repair that first case.
Thanks. m.