Issue with certian external clients not able to respond to our Skype rquest

We are having a strange issue with our Skype for Business.
Its been running just fine for sometime now but we have some external clients that are having an issue with our Skype ids.
What's happening is that we can send them a skype message and they receive it, but when the try to reply back to us, it eventually times out for them, and we don't get their reply.
Also when they bring up their list of other clients including ours, ours show up as status, Presence Unknown
Does anyone know what I can check to see why our IDs would be appearing to them as Presence Unknown?
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vmichAsked:
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Jeff GloverSr. Systems AdministratorCommented:
When you say external clients, do you mean from other organizations or your own users externally? Are they using SFB or just plain Skype (the commercial version) Are you allowing Open Federation or closed? Is (are) your edge server(s) set up correctly?
vmichAuthor Commented:
Yes other organizations not our users externally
How can I check if we are using open or closed federation?
Jeff GloverSr. Systems AdministratorCommented:
Get-csaccessedgeconfiguration. EnablePartnerDiscovery should be set to True. This will also tell you what policy you have set. you can then go into the Skype control panel and under Federation and External Access see the Policy settings.
  Also, you (and the other side) need to have SRV records for Sipfederationtls setup in DNS and an A record for the Access Edge IP. Lastly, if the others are Office 365 users of any domain, you need to put LyncOnline as a SIP Federated Provider, pointing to sipfed.online.lync.com (you set this in the SIP Federated Providers tab.
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vmichAuthor Commented:
Jeff,
I tried to run that command on the edge server but it errors out, the get-csaccessedgeconfuration
Is there something I need to do to get this to run?
vmichAuthor Commented:
I found the issue. The 2 internal certs on the edge server have expired. Now I need to track down the steps or a doc on how to renew both of them
Jeff GloverSr. Systems AdministratorCommented:
They should be from your internal ca. On an edge server, run the configuration wizard and step 3 should be to configure certificates. Select the internal adapter and generate csr. Since your edge should not be part of the domain, you will have to save the csr and get the certificate from your ca. Then install it and assign it to the edge server internal adapter. I use the edge pool as the dns name for the cert and the fqdn of both the edge servers as subject alternate names. I use one server to get the cert, then export it with the private key and import it into the other edge, using the config wizard to assign it to the internal adapter.
vmichAuthor Commented:
Jeff,
Is there a doc out there that shows these steps one at a time?
vmichAuthor Commented:
The issue I am having when trying to run through the deployment wizard, is the section where it tries to login into the edge server.
I cant seem to get it to login there
vmichAuthor Commented:
I got the certs renewed.
I also found out the original issue was because we are running Skype business 2015 and the client is running O365 so thye need to add our sip address to the federated on their skype server
vmichAuthor Commented:
I got the certs renewed.
I also found out the original issue was because we are running Skype business 2015 and the client is running O365 so thye need to add our sip address to the federated on their skype server

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