In order to debug your issue we need some information about your problem. Please follow this steps:
1. Inside NoMachine session open terminal and type ‘export’. Please, copy output and send us information
2. In node.cfg (/usr/NX/etc/node.cfg) please change ‘#SessionLogLevel 6’ to ‘SessionLogLevel 8’. After this reproduce your problem with no sound and send logs from server (all files from directory /usr/NX/var).
3. Also information from /proc/asoud/ can be usefull, please prepare archive (sudo tar -czf AlsaLog.tar.gz /proc/asoud) and send us AlsaLog.tar.gz archive.
4. Send all information to issues[at]nomachine[dot]com