Not sure why you're getting this particular error:
2022-03-22 18:30:33,231 [11692-Thread-0] WARN VASSAL.tools.ErrorDialog - Source: bdDinant Error: Unable to open board file
2022-03-22 18:40:57,726 [11692-Thread-0] ERROR VASSAL.tools.ProblemDialog -
java.util.zip.ZipException: zip END header not found
But, I can see from your log that you have a bunch of 'garbage' in your extensions folder and I wonder if the same holds true for your boards folder.
Specifically:
2022-03-22 18:29:41,926 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\BFP.mdx
2022-03-22 18:29:42,254 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Extension BFP v2.0 loaded
2022-03-22 18:29:42,254 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\BFP_v403.vmdx
2022-03-22 18:29:42,895 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Extension BFP_v403 v4.03 loaded
2022-03-22 18:29:42,895 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\BFP_v403.zip
2022-03-22 18:29:43,614 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Extension BFP_v403 v4.03 loaded
2022-03-22 18:29:43,614 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Extension Id for BFP_v403.zip (adf) conflicts with previously loaded extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\BFP_v403.vmdx
2022-03-22 18:29:43,629 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\BFPv5.01.vmdx
2022-03-22 18:29:45,295 [11692-AWT-EventQueue-0] INFO VASSAL.build.module.ExtensionsLoader - Extension BFPv5.01 v5.01 loaded
The BFP extensions are meant to replace previous versions.
Also, you have the zip file and the (v)mdx files in the folder too:
Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\Kreta.mdx
Extension Kreta v5.8.1 loaded
Loading extension C:\Program Files\VASSAL-3.6.5\VASL\Extensions\Kreta.zip
Extension Kreta v5.8.1 loaded
You should remove the *.zip files from the extensions folder (and maybe the boards folder?).
I also looks like you're installing all your VASL stuff into C:\Program Files\VASSAL-3.6.5\VASL\... which can sometimes trigger folder permissions issues.
Perhaps Doug will chime in with some more specifics to try. My suggestion would be to reset your boards to be something like
C:\Users\JohnF\VASL\boards
and see if a fresh start under your user folder sorts things out.