You’ve received reports that users have experienced issues with logging into an audio conference as the leader with their PIN and noticed that your Skype for Business Server 2015 front-end server has the following error written in the Lync Server logs:
Log Name: Lync Server
Source: LS UserPin Service
GetAndPublish web service failed due to an internal error. This may impact user sign-in.
Request Details - Entity: [firstname.lastname@example.org], Device Id: [6EFEFC0B-234D-55CA-A44F-061007CDAC2F], Authenticated User: [sip:email@example.com].
Additional Context: [CA_Failure: InternalError]
Cause: This is an unexpected failure
Re-start the web server. If you see this error continuously, examine the server traces and contact product support.
One of the reasons why this error would be thrown causing audio conferencing PIN login issues is if the front-end server is assigned a certificate that is configured with an unsupported Signature Algorithm such as the following example:
Signature algorithm: RSASSA-PSS
To correct the issue, either change the issuing certificate authority’s signature algorithm to a supported algorithm such as sha256RSA or obtain a certificate from an authority with a supported signature algorithm such as the following:
The above event log error will no longer be written and PIN sign in services will operate as expected once a certificate issued by a certificate authority with a supported signature algorithm is assigned