Try :

Navigate to /etc/init.d/openvas-server and openvas-manager and add time to this line:

time to wait for daemons death, in seconds

don't set it too low or you might not let openvassd die gracefully

DODTIME=5

make that DODTIME something like 15 or 20 for both openvas-server and openvas-manager.

start your scanner: service openvassd start then start the manager with the --rebuild argument. openvasmd --rebuild

Try :

Navigate to /etc/init.d/openvas-server and openvas-manager and add time to this line:

# time to wait for daemons death, in seconds
# don't set it too low or you might not let openvassd die gracefully
DODTIME=5

make that DODTIME something like 15 or 20 for both openvas-server and openvas-manager.

start your scanner: service openvassd start then start the manager with the --rebuild argument. openvasmd --rebuild