Ozeki crashing due to onvif.dll

I've been using the Ozeki Voip SDK for many years.

Today I've installed a WPF app by a client, and when running the app, it loads for a few seconds and then crashes.

This is what i get in fuslogvw.exe

*** Assembly Binder Log Entry  (9/7/2020 @ 8:14:40 AM) ***

The operation failed.
Bind result: hr = 0x80070002. The system cannot find the file specified.

Assembly manager loaded from:  C:\Windows\Microsoft.NET\Framework64\v4.0.30319\clr.dll
Running under executable  C:\Users\DSG\AppData\Local\Machshevet\MyApp.exe
--- A detailed error log follows.

=== Pre-bind state information ===
LOG: DisplayName = onvif, Version=2.2.190.0, Culture=neutral, PublicKeyToken=4812fb35129b8487
 (Fully-specified)
LOG: Appbase = file:///C:/Users/DSG/AppData/Local/Machshevet/
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = MyApp.exe
Calling assembly : VoIPSDK, Version=11.2.4.290, Culture=neutral, PublicKeyToken=4812fb35129b8487.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Users\DSG\AppData\Local\Machshevet\MyApp.exe.Config
LOG: Using host configuration file:
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config.
LOG: Post-policy reference: onvif, Version=2.2.190.0, Culture=neutral, PublicKeyToken=4812fb35129b8487
LOG: GAC Lookup was unsuccessful.
LOG: Attempting download of new URL file:///C:/Users/DSG/AppData/Local/Machshevet/onvif.DLL.
LOG: Attempting download of new URL file:///C:/Users/DSG/AppData/Local/Machshevet/onvif/onvif.DLL.
LOG: Attempting download of new URL file:///C:/Users/DSG/AppData/Local/Machshevet/onvif.EXE.
LOG: Attempting download of new URL file:///C:/Users/DSG/AppData/Local/Machshevet/onvif/onvif.EXE.
LOG: All probing URLs attempted and failed.

I scoured the web and my own pc, but cannot find any file named onvif.dll.

Why does it suddenly need this file that it never needed in the past? Or how can I find this file?

Or any other ideas?

Please advise, as my client is totally on standstill now.

Thanks!