New NAS from repurposed PC can't install plugins

[tricky]

So I've just installed the TrueNas software and created a pool on a brand new 4tb hard drive. I've created a dataset for media and then sub datasets for movies, tv etc.
I'm looking to copy all my files from my USB drive onto the new pool and run Plex from it. In time I will buy 2 extra hard drives as external back up for my PC's but just starting out at the moment and getting used to all this.

Now I'm trying to install Plex and getting this message when I choose the pool NAS:
[EFAULT] Failed to activate NAS : cannot open 'NAS': dataset does not exist

Code:

Error: Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/zfs.py", line 20, in run
    cp.check_returncode()
  File "/usr/local/lib/python3.9/subprocess.py", line 460, in check_returncode
    raise CalledProcessError(self.returncode, self.args, self.stdout,
subprocess.CalledProcessError: Command '['zfs', 'get', '-H', '-o', 'name,property,value', '-t', 'filesystem', 'all', 'NAS', 'boot-pool']' returned non-zero exit status 1.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/middlewared/plugins/jail_freebsd.py", line 1467, in activate
    iocage.activate(pool['name'])
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/iocage.py", line 379, in activate
    pool.deactivate_pool()
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/pools.py", line 51, in deactivate_pool
    Dataset(self.name, cache=self.cache).set_property(
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/dataset.py", line 38, in __init__
    self._properties = deepcopy(cache.datasets.get(self.resource_name))
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/cache.py", line 72, in datasets
    ioc_pool = self.iocage_activated_pool_internal(lock=False)
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/cache.py", line 42, in iocage_activated_pool_internal
    all_properties([p for p in pools], types=['filesystem'])
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/zfs.py", line 72, in all_properties
    data = run([
  File "/usr/local/lib/python3.9/site-packages/iocage_lib/zfs.py", line 22, in run
    raise ZFSException(cp.returncode, cp.stderr)
iocage_lib.zfs.ZFSException: cannot open 'NAS': dataset does not exist


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 138, in call_method
    result = await self.middleware._call(message['method'], serviceobj, methodobj, params, app=self,
  File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 1216, in _call
    return await self.run_in_executor(prepared_call.executor, methodobj, *prepared_call.args)
  File "/usr/local/lib/python3.9/site-packages/middlewared/main.py", line 1120, in run_in_executor
    return await loop.run_in_executor(pool, functools.partial(method, *args, **kwargs))
  File "/usr/local/lib/python3.9/concurrent/futures/thread.py", line 52, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.9/site-packages/middlewared/schema.py", line 977, in nf
    return f(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/middlewared/plugins/jail_freebsd.py", line 1469, in activate
    raise CallError(f'Failed to activate {pool["name"]}: {e}')
middlewared.service_exception.CallError: [EFAULT] Failed to activate NAS : cannot open 'NAS': dataset does not exist

So I've then been looking at various post's and thought I'd try to install a jail which then throws up the message above.

Please for the love of GOD what am I doing wrong?!

 

[Evertb1]

First start by reading the Forum rules. There is a section about what you should do before you post.
Second I can't help but wonder what made you choose for TrueNAS? Most TrueNAS users have gone to FreeNAS/TrueNAS because of the fact that TrueNAS makes use of the rock solid ZFS file system. Using ZFS comes with some requirements (a lot actually if tyou take your dat serious). Using a repurposed PC, a single drive pool etc. makes me doubt that you started well informed with this road you are on . If you ask me you have a lot of reading to do before you go on. Introduction to ZFS for example. Ofcourse reading the TrueNAS manual would not harm eather.