Error when connecting: "The procedure entry point (name) could not be located in the dynamic link library (name.dll)." (4310934)

The following error is displayed when connecting to a database. Unable to connect.

"The procedure entry point ons_init_wconfig_ctx could not be located in the dynamic link library oraons.dll."

or

"The procedure entry point knclgLcrRowGetBindVariables could not be located in Dynamic Link Library oracommon11.dll

or

"The procedure entry point ons_error_set could not be located in the dynamic link library C:\oracle\app\product\12.1.0\client_1\BIN\oraclient12.dll"

Appears to be conflict between two or more installed Oracle Homes.

The path of the Oracle Client user wants to use is not in the beginning of the PATH system environment variable. 

RESOLUTION 1:

Swap entries in the system environment variable 'Path' so that the client being used in Toad is the first entry.

To check which Oracle Home is being used by Toad, make a connection and then go to Help | Support Bundle

Look for :

To edit the system environment variable PATH:

For example if C:\oracle\product\11.2.0\client_1  ***** This is the home currently used by Toad *****

Then place 'C:\oracle\product\11.2.0\client_1\bin;' at the beginning

C:\oracle\product\11.2.0\client_1\bin;C:\oracle\product\11.2.0\client_2\bin....

RESOLUTION 2:

Restart Toad.  Select the Oracle Client Home indented to use under "Connect Using:", and then check the option "Make this the TOAD default home".  Try connecting again.

RESOLUTION 3:

Uninstall the Oracle Clients not being used so there's only one valid Oracle Client to connect with.