Connections to Oracle - How to determine which Oracle client is used by SSDT and SSIS

I have connection to Oracle from SSDT and SSIS on 1 desktop that is failing when tested with error  "ORA-06413:  Connection not open"

There are multi Oracle clients on this desktop, 32 bit, 64 bit, and 12c. We can TNSping successfully and tnsnames.ora is good.  How do I know which Oracle client is being select by SSDT for SSIS and failing?  Can I control which Oracle client is used? 32bit, 64bit, 12c, or older?  

I have other desktops with no issues and a similar setup.

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Tony C