I opened all the files in the com_vehiclemanager folder.
I looked for: "Sanity" in all opened files.
Then replaced
} else if (version_compare(JVERSION, "1.6.0", "ge" && version_compare(JVERSION, "3.5.0", "lt"
with
} else if (version_compare(JVERSION, "1.6.0", "ge" && version_compare(JVERSION, "4.5.0", "lt"
All this line does is trick this version check to look for Joomla version 4.5 instead of 3.5.
If you still get the error JVERSION, "3.5.0" must still be in more atleast one place.
Remember this is only a temporary fix until they release a new version of vehicle manager.
Here is a site running Joomla 3.5 that is used this hack on.
www.velocitybarbados.com/home