We have recently found a scenario in HC10 panel where same error was thrown while adding SIP Users in Bulk... To resolve the case, you should ensure that SIP Address is all in lowercase(No Upper Case). Hopefully this shall resolve the case. In case if issue persists then you may send an email to
support@hostingcontroller.com in order to get further help regarding this case.
We would get this case resolved in the forthcoming installer of HC10.16.