For me (3.7) the registry key fix seems to have worked.
https://stackoverflow.com/questions/33761919/tls-1-2-in-net-framework-4-0 (about halfway down)
- Set the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319: SchUseStrongCrypto to DWORD 1
Of course that fix requires .net 4.0 or 4.5. I don't recall what nopCommerce version switched to 4.0 so it may not work on older versions.
I saw the Reg fix suggestion at stackoverflow. I personally did not like it as:
- The site will break again if you change the hosting
- You are forcing all application on the server to go TLS 1.2. That might not be a good idea.
- There would be errors on your localhost. Surely it is not a good idea to apply the reg fix on your development machine
I preferred to switch the nopCommerce site to TLS 1.2.