Nfs – mount.nfs: an incorrect mount option was specified

I'm trying to mount an NFS volume on a centos 7.2 server:

When I try to mount the NFS share point, this is the response I get back:

[root@web1:~] #mount -t nfs nfs1.example.com:/var/nfs/home /home
mount.nfs: an incorrect mount option was specified

I checked and I have nfs-utils-1.3.0-0.21.el7.x86_64 installed on both machines. Both the nfs client and the nfs server OSes are Centos 7.2

To troubleshoot this, I reduced the listings in the /etc/exports file on the NFS server to just the following:

/var/nfs/home web1.example.com(rw,sync,no_root_squash,no_all_squash)

If I do a showmount from the server I'm trying to mount the nfs share on, this is what I see:

[root@web1:~] #showmount -e nfs1.example.com
Export list for nfs1.example.com:
/var/nfs/home web1.example.com

If I do a mount -v this is what I get:

[root@web1:~] #mount -v -t nfs nfs1.example.com:/var/nfs/home /home
mount.nfs: timeout set for Fri Jan 13 11:04:19 2017 mount.nfs: trying text-based options 'vers=4,addr=162.xxx.xxx..94,clientaddr=162.xxx.xxx.6'
mount.nfs: mount(2): Invalid argument mount.nfs: an incorrect mount option was specified

In dmesg I find:

[44428.405419] nfsd: last server has exited, flushing export cache

And I'm seeing this in dmesg:

[ 7.373186] FS-Cache: Netfs 'nfs' registered for caching
[ 7.422181] Key type dns_resolver registered
[ 7.456581] NFS: Registering the id_resolver key type
[ 7.462309] Key type id_resolver registered
[ 7.462386] Key type id_legacy registered
[ 7.514441] SELinux: initialized (dev 0:40, type nfs4), uses genfs_contexts
[ 8.474503] NFSD: starting 90-second grace period (net ffffffff819a29c0) –
[ 16.952180] perf samples too long (2623 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
[ 24.429251] SELinux: initialized (dev tmpfs, type tmpfs), uses transition SIDs
[ 38.368207] perf samples too long (5162 > 5000), lowering kernel.perf_event_max_sample_rate to 25000
[ 38.427323]

Not specifying -t nfs in the command gives the same result:

[root@nfs1:~] #mount nfs1.example.com:/var/nfs/home /home
mount.nfs: an incorrect mount option was specified

These are the nfs file systems I have:

[root@nfs1:~] #grep nfs /proc/filesystems
nodev   nfsd
nodev   nfs
nodev   nfs4

Here are the modules loaded for nfs:

[root@nfs1:~] #lsmod | grep ^nfs
nfsv4                 474203  0
nfs                   241266  1 nfsv4
nfsd                  284378  13
nfs_acl                12837  1 nfsd

It's not a firewall issue because I get the same exact failure when I run the mount command from the NFS server itself. It gets the same error that it's clients do.

I should stress that this did at one time work fine. But now it's broken to the point where it can't be used.

Can someone please help me troubleshoot this? I'm really stuck at this point.