What OS are you connecting from? What Linux distro, version and desktop environment are you connecting to? I understand you connect once and everything is ok. Then you disconnect and reconnect immediately afterwards and you see a white screen?
Logs from the Linux server you are connecting to would be useful in that case.
See here on how to locate them once you’ve reproduced the issue, https://www.nomachine.com/AR10K00697
Please send the logs to forum[at]nomachine[dot]com using the title of this forum’s thread as the mail’s subject.