You can check if the server is running in NFS Manager itself:
Hit the Test Server button in NFS Manager:
Enter the IP of the server (either 127.0.0.1 or the interface IP e.g. 192.168.0.5) and hit "Test".
If the NFS server is running you get the following result:
Some of the ports depend on your configuration. The above example shows the standard ports.
From remote you can check this by executing nmap. A running NFS server looks like this:
host:~ user$ nmap ip
Starting Nmap 7.30 ( https://nmap.org ) at 2016-12-16 01:26 CET
Nmap scan report for IP
Host is up (0.00015s latency).
Not shown: 967 closed ports, 27 filtered ports
PORT STATE SERVICE
111/tcp open rpcbind
1001/tcp open unknown
1021/tcp open exp1
1023/tcp open netvenuechat
2049/tcp open nfs
If your firewall is off, then either your NFS server or client (or both) are configured incorrectly.