Unable to start ipython kernel Python 3.8.5

I am unable to start my notebook on my newly installed python environment. The kernel fails to start giving me this error:

Traceback (most recent call last):
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/web.py", line 1704, in _execute
    result = await result
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
    yielded = self.gen.throw(*exc_info)  # type: ignore
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/notebook/services/sessions/handlers.py", line 69, in post
    model = yield maybe_future(
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
    value = future.result()
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
    yielded = self.gen.throw(*exc_info)  # type: ignore
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/notebook/services/sessions/sessionmanager.py", line 88, in create_session
    kernel_id = yield self.start_kernel_for_session(session_id, path, name, type, kernel_name)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
    value = future.result()
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
    yielded = self.gen.throw(*exc_info)  # type: ignore
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/notebook/services/sessions/sessionmanager.py", line 100, in start_kernel_for_session
    kernel_id = yield maybe_future(
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
    value = future.result()
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/notebook/services/kernels/kernelmanager.py", line 176, in start_kernel
    kernel_id = await maybe_future(self.pinned_superclass.start_kernel(self, **kwargs))
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/jupyter_client/multikernelmanager.py", line 184, in start_kernel
    km, kernel_name, kernel_id = self.pre_start_kernel(kernel_name, kwargs)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/jupyter_client/multikernelmanager.py", line 169, in pre_start_kernel
    km = self.kernel_manager_factory(connection_file=os.path.join(
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/jupyter_client/multikernelmanager.py", line 83, in create_kernel_manager
    km = kernel_manager_ctor(*args, **kwargs)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/config/configurable.py", line 82, in __init__
    super(Configurable, self).__init__(**kwargs)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/traitlets.py", line 1080, in __init__
    super_kwargs[key] = value
  File "/usr/lib/python3.8/contextlib.py", line 120, in __exit__
    next(self.gen)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/traitlets.py", line 1214, in hold_trait_notifications
    self.notify_change(change)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/traitlets.py", line 1227, in notify_change
    return self._notify_observers(change)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/traitlets.py", line 1264, in _notify_observers
    c(event)
  File "/home/doctoq/Desktop/Dev/Policy-Gradient/venv/lib/python3.8/site-packages/traitlets/traitlets.py", line 888, in compatible_observer
    return func(self, change)
TypeError: _kernel_spec_manager_changed() takes 1 positional argument but 2 were given

I'm on Ubuntu 20.04 with python 3.8.5. I've only installed 'notebook' with pip (20.3.3) and get this error when opening a new notebook.

Here's my package list:

(venv) doctoq:Policy-Gradient$ pip list
Package             Version
------------------- -------
argon2-cffi         20.1.0
async-generator     1.10
attrs               20.3.0
backcall            0.2.0
bleach              3.2.1
cffi                1.14.4
decorator           4.4.2
defusedxml          0.6.0
entrypoints         0.3
ipykernel           5.4.2
ipython             7.19.0
ipython-genutils    0.2.0
jedi                0.17.2
Jinja2              2.11.2
jsonschema          3.2.0
jupyter-client      6.1.9
jupyter-core        4.7.0
jupyterlab-pygments 0.1.2
MarkupSafe          1.1.1
mistune             0.8.4
nbclient            0.5.1
nbconvert           6.0.7
nbformat            5.0.8
nest-asyncio        1.4.3
notebook            6.1.6
packaging           20.8
pandocfilters       1.4.3
parso               0.7.1
pexpect             4.8.0
pickleshare         0.7.5
pip                 20.3.3
prometheus-client   0.9.0
prompt-toolkit      3.0.9
ptyprocess          0.7.0
pycparser           2.20
Pygments            2.7.3
pyparsing           2.4.7
pyrsistent          0.17.3
python-dateutil     2.8.1
pyzmq               20.0.0
Send2Trash          1.5.0
setuptools          51.1.1
six                 1.15.0
terminado           0.9.2
testpath            0.4.4
tornado             6.1
traitlets           5.0.5
wcwidth             0.2.5
webencodings        0.5.1
wheel               0.36.1

I can't find this issue anywhere. I tried installing older versions of 'notebook' and 'traitlets' but I get the same issue.

Does anyone have an idea? Thanks!