This issue occurs if the meeting ID contains the uppercase "I" in the meeting URL.
Note This issue occurs because, in Turkish, the uppercase of the character "I" is "İ," and the lowercase of the character "I" is "i." "i" and "I" are not a matched pair any longer. Therefore, "i" and "I" are not equal in the case-insensitive comparison.
To resolve this issue, install the June 2015 cumulative update 6.0.9319.55 for Microsoft Skype for Business Server 2015, Web Components server.
To work around this issue, change the uppercase "I" to the lowercase "i" in the meeting URL, and then you can join the meeting through its URL successfully.