I have successfully upgraded PB 10.5/ PB 11.5 applications to PB 2019 R3 2703. Both versions connect SQL Server database (SQL 2012 SP3) through OLE DB only. My SQLCA parameters are (from my ini file) :
DBParm = "PROVIDER='SQLOLEDB',DATASOURCE='computername\SQL2012',PBMaxBlobSize='100000',PBMaxTextSize='100000',PROVIDERSTRING='Database=dbname'"
I haven't installed mssoledbsql, connections are through OLE DB alone.
I used to install 64 bit sql server exe, if the windows is 64 bit else will install 32 bit sql server. For clients there is no need to install any drivers and OLE DB is available by default in all windows.
Can you check the connection parameters?
Isn't this driver only already available if you have Office installed?