You can try stopping and starting the SVXLink service from the command line with the following commands:
service svxlink stop
service svxlink start

If you want to check the results of this you can open another terminal window and issues the following command to watch the log file real time:
tail -f /var/log/svxlink

You may want to check your port setting to make sure you audio card is set correctly. Also just try changing a setting and rebuilding the config files which will restart the service afterwards.

Hope that helps.