Cannot connect to remote library

When Roon Remote is started on my laptop it does not get passed the message “looking for remote libraries…”
From the laptop I can connect to Roon Server via ssh. A restart of the service or reboot of the server had no effect. Yesterday all was working fine.

Roon 1.2 (build 154) stable

Roon Server
Hardware: Intel NUC6 i5, 32GB RAM, 256GB M.2 SSD
OS: Ubuntu 16.04.1 LTS x86_64

Roon Remote
Hardware: HP laptop EliteBook 8570w i7 16GB RAM
OS: Windows 10 Enterprise

Roon Bridge
Hardware: Odroid C1+ ARMv7
OS: Ubuntu 14.04.5 LTS
DAC connected via USB

All conected via wired Ethernet

QNAP NAS NFS share mounted on the server

● roonserver.service - RoonServer
Loaded: loaded (/etc/systemd/system/roonserver.service; enabled; vendor preset: enabled)
Active: active (running) since wo 2016-08-10 22:06:10 CEST; 29min ago
Main PID: 7442 (
CPU: 1min 4.005s
CGroup: /system.slice/roonserver.service
├─ 7442 /bin/bash /opt/RoonServer/
├─ 7447 /opt/RoonServer/Mono/bin/RoonServer --debug --gc=sgen --server RoonServer.exe
├─10014 /opt/RoonServer/Mono/bin/RoonAppliance --debug --gc=sgen --server RoonAppliance.exe -watchdogport=44365
├─10016 /opt/RoonServer/Server/processreaper 10014
└─10045 /opt/RoonServer/Mono/bin/RAATServer --debug --gc=sgen --server RAATServer.exe

aug 10 22:34:29 mediapc[7442]: Initializing
aug 10 22:34:29 mediapc[7442]: Started
aug 10 22:34:37 mediapc[7442]: Not responding
aug 10 22:35:07 mediapc[7442]: Error
aug 10 22:35:09 mediapc[7442]: Initializing
aug 10 22:35:09 mediapc[7442]: Started
aug 10 22:35:17 mediapc[7442]: Not responding
aug 10 22:35:48 mediapc[7442]: Error
aug 10 22:35:50 mediapc[7442]: Initializing
aug 10 22:35:50 mediapc[7442]: Started

Problem solved after a reboot of the NAS