We have Skype for business on-premises setup and use office 365 for emails.
However, we are having problems with contacting Skype users from our Skype for business app. I have tested sending invites but they are not getting to the users both ways. I can search Skype users which appears but when send and invite nothing gets sent.
Have made sure that Skype admin is setup so that external communication is set to "On except for blocked domains" is there something that I have missed?
I have tested connection with other organisations also using Skype for business, that seems to be working for some organisations but not all, but I think that they need to add us into there allowed domain list. Any help would be much appreciated.