Error: Could not find or load main class com.intel.bts.BtsApp

I have hit the same problem with the Stratix10 DX board test system (BTS) files. I'm running Ubuntu and I see the same same error: "Error: Could not find or load main class com.intel.bts.BtsApp" running any of the *.sh scripts in the board_test_system subdirectory of the devkit's examples.

This is the default version of the bts launcher:

#!/bin/sh
if [ "$QUARTUS_ROOTDIR" == "" ]; then
export QUARTUS_ROOTDIR=/tools/acds/15.1.2/current.linux/linux64/quartus
echo "Use default QUARTUS_ROOTDIR: $QUARTUS_ROOTDIR"
fi
export PATH=$QUARTUS_ROOTDIR/linux64/jre64/bin:$PATH
java -Xmx256m -jar bts.jar

I don't think the way that script determines QUARTUS_ROOTDIR is a general solution, but even when I 'fix it' for my installation the command: java -Xmx256m -jar bts.jar gives the same error above.

Any suggestions on how to fix or debug this?