A quick way to solve issues with SSTP issues when attempting to connect VPN to server 2008 and receiving error 619...
Run command prompt as administrator.
netsh http delete ssl 0.0.0.0:443
netsh http delete ssl [::]:443
reg delete HKLM\SYSTEM\CurrentControlSet\Services\SstpSvc\Parameters /v SHA256CertificateHash /f
net stop sstpsvc /y
net start remoteaccess
Now try connecting the VPN again. Good luck!