I've also tried things like:
1. conda update --all
2. conda uninstall anaconda
3. conda install anaconda
4. conda update anaconda-navigator
5. anaconda-navigator --reset
6. deleted .condarc file from the main directory
7. conda install pyqt5
8. conda install pyqtwebengine
but none of them worked
anaconda version 2020.2 python version 3.7.6