If you or one of your users are getting an error when opening the SightCall Widget in Salesforce that says
"An error occured...
Internal Server Error"
You should check to make sure that their email has not been used as a login item in another tenant at any point. This could include a demo tenant that you used at first, or perhaps your company has both a Salesforce/Integrated tenant and a "Standalone" one. You will have to delete and re-create the user with a different login in order for the SightCall Salesforce widget to connect succesfully.
If that doesn't resolve it or you are unable to find any other accounts, please contact SightCall Support who will be able to help in this matter.