A couple of things - do you see your process still running (ex. with `top`?) With a 20G Bloom filter, I'd also suggest running with multiple threads - so using -j. Also, you can use -v to have verbose output.
If you re-run with those conditions, and see that the process is still doing nothing, I would suggest running a smaller test with a couple of scaffolds and some reads. That way, you can ensure that your installation is working correctly.
Thanks for your interest in ABySS!