Not able to Sign in into Skype for Business

Hi Ankur,

Via the error message, it seems that the username or password of your Skype for Business account is incorrect. So, you may firstly re-confirm this. Secondly, I’d like to confirm whether it is the first time when you tried signing into Skype for Business and got the issue. If so, I suggest you check whether the related DNS record(s) (especially Skype for Business Autodiscover) of the domain has been added correctly. For more information, you can refer to https://support.office.com/en-us/article/Create-DNS-records-at-GoDaddy-for-Office-365-f40a9185-b6d5-4a80-bb31-aa3bb0cab48a?ui=en-US&rs=en-US&ad=US#bkmk_add_cname (CNAME record, lyncdiscover). You may provide your Skype for Business account in the Private Message (PM) for checking. 

If it is not the first time, I mean, it worked well before. I recommend you clear the cache and re-sign into it. To clear the Skype for Business cache, you can delete sip_profileName folder. The detailed steps are: 
1. Exit Skype for Business.
2. Open Run bad and type  in %AppData%. Make sure you're in the AppData directory and navigate to \Local\Microsoft\Office\15.0\Lync\ for Skype for Business and Lync 2013 or Local\Microsoft\Office\16.0\Lync for Skype for Busines 2016
3. Delete all files in Tracing folder. Do not delete the folder itself.
4. Clear DNS cache: in Command Prompt run ipconfig /flushdns command.

Regards,
Alan