The underlying connection was closed: an unexpected error occurred on a send” during PaperVision Tools login
Article ID: PT000021
In a recent update, Microsoft introduced a security change to TLS (Transport Layer Security) behaviour that causes the first TLS record after the handshake to be split. This breaks some applications that were written based on the .NET Framework and not explicitly written to use TLS version 1.1 or later. While this issue has been fixed and released as part of PV Tools R84.1, it is possible to force earlier versions of the application to use the newer TLS protocols and circumvent the issue via use of these registry keys:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319] "SchUseStrongCrypto"=dword:00000001 [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319] "SchUseStrongCrypto"=dword:00000001
To automate this process, run the following commands in an elevated command prompt. For simplicity these commands have been separated by architecture, but there is no harm in running both if necessary.
REG ADD HKLM\SOFTWARE\Microsoft\.NetFramework\v4.0.30319 /v SchUseStrongCrypto /t REG_DWORD /d 1
REG ADD HKLM\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319 /v SchUseStrongCrypto /t REG_DWORD /d 1
This issue, its cause, and the solution provided here is documented in detail in the Microsoft Support article here.