Today I have a very appetizing mushroom. Perhaps you have had at anytime a problem with your Skype to Skype for Business integration.
I describe the problem:
Some users advise you that they can contact with Skype users, but Skype users can’t view presence and doesn’t have chat with Skype for business users, for example:
If you have tested your deployment, and you followed all steps from Technet guidance: https://technet.microsoft.com/en-us/library/dn705313.aspx
Also you checked your firewall and everything is allowed. Keep calm, you are not crazy. Your environment are correctly configured, but you have some users that are using Lync 2013 (With or without skype for business interface). Please, follow next steps to solve your issue.
Check if your users with those clients have next configuration:
If not, please apply it and try again.
Open your client options and go to ‘alerts’. On ‘contacts not using Skype for Business’ menu, check ‘allow anyone to contact me’. The problem will be resolved.
I hope this information will be useful for you.