Question: I'm getting this error when connecting Microsoft OLE DB Driver 19 for SQL Server  &  Microsoft ODBC Driver 18.x for SQL Server.

The certificate chain was issued by an authority that is not trusted

What is the fix for this error ?

Answer:

Step 1: Check if sql server Force Encryption is set to No .   There are different wasys to check such as How to check SSL encryption is enabled on SQL Server with Powershell    & How to check a SQL Server connection is encrypted with SSL

here is an example

DECLARE @force_encryption INT

EXEC xp_instance_regread 'HKEY_LOCAL_MACHINE', 'Software\Microsoft\Microsoft SQL Server\MSSQLServer\SuperSocketNetLib', 'ForceEncryption', @force_encryption OUTPUT

SELECT CASE WHEN @force_encryption = 1 THEN 'Force Encryption = True ' ELSE 'Force Encryption = False' END

Step 2: Check if the client connection string explcitly states an encryption property value , or DSN

If both Step 1 & Step 2 return No , than the likelihood is your hitting the new default behaviour of the client drivers mentioned in your question :Microsoft OLE DB Driver 19 for SQL Server  &  Microsoft ODBC Driver 18.x for SQL Server.

These new versions of drivers assume the data encryption is on by DEFAULT - therefore  upon connection , there is an attempt to validate the certificate . 

There's a few different options to fix the issue

1) Rollback to MS ODBC Driver 17 for SQL Server

2) Review the connection string - does it specify Yes for Encryption , change it to No. 

If Data Souce Name (DSN) - review the encryption setting - is set at mandatory ? Change to Optional