I struggled with this as well and might be able to shed some more light on it.
In addition the non-starting VMs, I found another oddity that even though I started Fusion from the dock icon it would open a new dock icon. Looking at the Fusion process in the Activity Manager, I found that the process that ran was not /Applications/VMWARE Fusion.app but /private/var/folders/wv/61rq21kn77s3_ggcn68bmj3w0000gn/T/AppTranslocation/something-something-something/d/VMware Fusion.app/Contents/MacOS/VMware Fusion
So it seems that Fusion's installation is triggering the App Translocation https://lapcatsoftware.com/articles/app-translocation.html
My Fix: Moving the app from /Applications to my HOME folder and then moving it back to /Applications by using Finder. Using Finder is the important step!
On the next start, I got the security prompt about the kext files and allowed them in the security options. And viola, no more "internal error", my VMs start again.
So for some reason your install is triggering this for some people. Happened also after a reinstallation attempt as outlined above. This was with Fusion 10.0.1, never had the release version installed.