Test via Powershell

$connectionString = 'Data Source=%servername%\PROD;Initial Catalog=%dbame%;User ID=passwordstate_user;Password=%password%'
$sqlConnection = New-Object System.Data.SqlClient.SqlConnection $connectionString
$sqlConnection.Open()

Check web.config of Passwordstate

<system.web>
    <compilation targetFramework="4.7.2"/> 
    <httpRuntime targetFramework="4.7.2" />
</system.web>

Configure for strong cryptography

And Reboot

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v2.0.50727]
      "SystemDefaultTlsVersions" = dword:00000001
      "SchUseStrongCrypto" = dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
      "SystemDefaultTlsVersions" = dword:00000001
      "SchUseStrongCrypto" = dword:00000001

For 32-bit applications that are running on 64-bit OSs, update the following subkey values:

RegistryCopy

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727]
      "SystemDefaultTlsVersions" = dword:00000001
      "SchUseStrongCrypto" = dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319]
      "SystemDefaultTlsVersions" = dword:00000001
      "SchUseStrongCrypto" = dword:00000001

Confirm SQL Trace

CREATE EVENT SESSION [tls] ON SERVER
ADD EVENT sqlsni.trace(
WHERE (([sqlserver].[like_i_sql_unicode_string]([text],N'%Handshake%TLS1.0%'))
OR ([sqlserver].[like_i_sql_unicode_string]([text],N'%Handshake%TLS1.1%'))
OR ([sqlserver].[like_i_sql_unicode_string]([text],N'%Handshake%TLS1.2%'))
))
ALTER EVENT SESSION [tls] ON SERVER
ADD TARGET package0.ring_buffer(SET max_events_limit=(100000),max_memory=(10240))
WITH (MAX_MEMORY=10240 KB,STARTUP_STATE=ON)
GO
ALTER EVENT SESSION tls ON SERVER STATE = START;