Hi,
I am using PL/SQL Developer version 11 on Windows 10 64bit and I keep getting the following error message:

"Initialization error
Could not initialize
C:\Oracle\product\instantclient_12_1\oci.dll

OCIDLL forced to C:\Oracle\product\instantclient_12_1\oci.dll
LoadLibrary(C:\Oracle\product\instantclient_12_1\oci.dll)
returned 0
"

. I have installed the following versions of the Oracle Client:
- Instant Client 11.3 (32bit)
- Instant Client 12.1 (32bit)
- Oracle client 11.2 (32bit)
I configure the IDE under tools/preferences to set the Oracle home and OCI library to point to the above client.
I also set the TNS_ADMiN environment variable.
All of the above to no avail. Please help.

Support Info below:

PL/SQL Developer
Version 11.0.4.1788 (64 bit)
02.100339 - 100 user license
Service Contract: 4/1/2016
Windows 10 Build 10586

Physical memory : 16,696,464 kB (13,123,296 available)
Paging file : 19,186,832 kB (15,484,372 available)
Virtual memory : 137,438,953,344 kB (137,438,645,220 available)

Parameters
C:\Program Files\PLSQL Developer\plsqldev.exe

Preferences
Session mode: Multi
OCI Library: C:\Oracle\product\instantclient_12_1\oci.dll
Use OCI7: False
Allow Multiple Connections: True

Preference Files
C:\Users\Roland\AppData\Roaming\PLSQL Developer\Preferences\default\Default.ini
C:\Users\Roland\AppData\Roaming\PLSQL Developer\Preferences\Roland\default.ini

License File
C:\Users\Roland\AppData\Roaming\PLSQL Developer\aalf.dat

Debug file
C:\Users\Roland\AppData\Roaming\PLSQL Developer\PlSqlDev.elf

Plug-Ins
*Active Query Builder (C:\Program Files\PLSQL Developer\PlugIns\ActiveQueryBuilder.dll)
*PL/SQL Documentation (plsqldoc) (C:\Program Files\PLSQL Developer\PlugIns\plsqldoc.dll)
*Red Gate Deployment Plug-In (C:\Program Files\PLSQL Developer\PlugIns\RedGate.dll)
(* is Active)

Aliases

Homes

DLLs
C:\Oracle\product\instantclient_12_1\oci.dll

TNS File

Using
Home:
DLL: C:\Oracle\product\instantclient_12_1\oci.dll
OCI: not initialized

Monitor
PixelsPerInch = 120

Id = 0
Primary = True
Handle = 65537
Left = 0
Top = 0
Width = 1920
Height = 1080

MainFormOnTaskbar = False