Hi Marco,
Not sure if this has ever been resolved.
But we recently installed Oracle Client 19 64bit and PLSQL Developer 11 64bit on a Windows 10 PC encountered the same problem.
Here's the content of the Support Info screen:
PL/SQL Developer
Version 11.0.0.1762
01.100458 - 20 user license
Service Contract: None
Windows 8 (64-bit) 6.2 Build 9200
Physical memory : 2,097,152 kB (2,097,152 available)
Paging file : 4,194,304 kB (4,194,304 available)
Virtual memory : 2,097,024 kB (1,895,636 available)
Parameters
C:\Program Files (x86)\PLSQL Developer\plsqldev.exe
Preferences
Session mode: Multi
OCI Library:
Use OCI7: False
Allow Multiple Connections: True
Preference Files
C:\Program Files (x86)\PLSQL Developer\Preferences\Default\Default.ini
C:\Users\A0814538\AppData\Roaming\PLSQL Developer\Preferences\A0814538\default.ini
License File
C:\Users\A0814538\AppData\Roaming\PLSQL Developer\aalf.dat
Debug file
C:\Users\A0814538\AppData\Roaming\PLSQL Developer\PlSqlDev.elf
Plug-Ins
*Active Query Builder (C:\Program Files (x86)\PLSQL Developer\PlugIns\ActiveQueryBuilder.dll)
*PL/SQL Documentation (plsqldoc) (C:\Program Files (x86)\PLSQL Developer\PlugIns\plsqldoc.dll)
*Red Gate Deployment Plug-In (C:\Program Files (x86)\PLSQL Developer\PlugIns\RedGate.dll)
*Version Control Interface 1.2 (C:\Program Files (x86)\PLSQL Developer\PlugIns\VCS.dll)
(* is Active)
Aliases
Homes
DLLs
D:\app\Oracle\product\19.0.0\client_1\bin\oci.dll
TNS File
Using
Home:
DLL:
OCI: not initialized
Monitor
Id = 0
Primary = True
Handle = 65537
Left = 0
Top = 0
Width = 1366
Height = 768
MainFormOnTaskbar = False