Jupyter notebook does not launch (ImportError: DLL load failed while importing)

Recently my jupyter notebook stopped launching. When I try the command jupyter notebook from anaconda prompt but it gives error

Traceback (most recent call last):
File "C:UsersDellanaconda3Scriptsjupyter-notebook-script.py", line 6, in
from notebook.notebookapp import main
File "C:UsersDellanaconda3libsite-packagesnotebooknotebookapp.py", line 51, in
from zmq.eventloop import ioloop
File "C:UsersDellanaconda3libsite-packageszmq_init_.py", line 50, in
from zmq import backend
File "C:UsersDellanaconda3libsite-packageszmqbackend_init_.py", line 40, in
reraise(*exc_info)
File "C:UsersDellanaconda3libsite-packageszmqutilssixcerpt.py", line 34, in reraise
raise value
File "C:UsersDellanaconda3libsite-packageszmqbackend_init_.py", line 27, in
ns = select_backend(first)
File "C:UsersDellanaconda3libsite-packageszmqbackendselect.py", line 28, in select_backend
mod = import(name, fromlist=public_api)
File "C:UsersDellanaconda3libsite-packageszmqbackendcython_init.py", line 6, in
from . import (constants, error, message, context,
ImportError: DLL load failed while importing error: The specified module could not be found.

I even tried reinstalling anaconda and upgraded to python 3.8.3 on windows 10 but still get the same error. When I tried to check jupyter notebook’s version it said that ipykernel and some other things were not installed. jupyter --version gives me this:

jupyter core : 4.6.3
jupyter-notebook : 6.1.1
qtconsole : 4.7.6
ipython : 7.18.1
ipykernel : not installed
jupyter client : not installed
jupyter lab : not installed
nbconvert : 5.6.1

But installing ipykernel with conda install ipykernel says

All requested packages already installed.

I also tried ipython kernel install --name <env_name> --user but this gives another dll error.

Reading some other problems in stackoverflow I went and checked my enviroment variables.

Is there a problem with this environment variable. Please help.

Screenshot of the anaconda prompt with error.

Edit: The anaconda navigator does not launch either. anaconda-navigator on the anaconda prompt gives another error:

I also tried:

conda install qt --force
conda install pyqt --force

But that did’nt help. Does previously installed anaconda cause such error?