Ross will have to help you on this.   I thought maybe it might be permissions but there is nothing at all not even a ghost error icon.  I never seen that before. 

Actually, only the icon image is missing. The icons are still functioning.
I have tried to uninstall and delete messages plugin and install it again, but nothing changed.

yes very strange, usually if its a permission issue you will see a ghost icon there but theres nothing.  

How about any new plugins, have you recently installed any?  When did this start happening?

Also have you checked the console to see if any errors show?  

Do you have debug or dev mode on?

I dont know of a setting in admin for this, ill have to look, there might be.

yeah those are all default oxwall icons... 

just out of curiosity do you have the plugin config set for mails, chats, or both?

those icons are blocked by mode security. it should be disabled according to our server requirements: http://www.oxwall.org/hosting

contact your hosting provider to disable it. 

ahhhh thanks ross i didnt know that... good info, now i do.. :)

Hi All, would it be possible for us to trace the issue on these missing icon? why it was blocked by mod_security?

Lawntor, each hosting company has their own security rules. You need to contact your host to get  more information on why icons were blocked on your server