Thanks for the logs.
I'm mostly interested in the logs for 0.8.24. There won't be any modifications on top of 0.8.15.
Fortunately, log.txt.1 is new to recent versions so it contains 0.8.24 log.
The error there is the following:
System.Exception: Environment variable PYLONC_ROOT not found. Install the pylon C Runtime.
at PylonC.NET.Bootstrapper.Initialize()
at PylonC.NET.Pylon..cctor()
The way it is supposed to work is: Kinovea embeds a "wrapper" library published by Basler that acts as a bridge between the program and the rest of the Pylon stuff installed on the machine. This library looks for the environment variable to know where the rest of the Pylon DLL are located.
Please check if you have such an environment variable, I imagine it should be set during Pylon installation. (Right click My Computer > Properties > Advanced system settings > Advanced > Environment variables). I will look on my machine tonight to confirm.
By thumbnails I was referring to the camera thumbnails from the camera explorer. Considering the nature of the failure I would guess there is no thumbnail at all though.
