conda 4.7.7 ->4.6 - Collecting package metadata (current_repodata.json) - (channel conda-forge) ipywidgets-5.2.3-py36_0 due to InvalidSpec: ==1.*

This solution helped my system, set a conda config parameter conda docs

conda config --set allow_conda_downgrades true
conda install conda=4.6.11

It works all right again.

I work with win10 1903, python 3.7 and conda 4.7.

I downgrade conda to 4.6.14 and reboot. Then everything works normally.

A new version of conda is out! version 4.7.10 It is out on the canary channel. Run the following command and check whether it fixes the issue:

conda update conda -c conda-canary

or:

conda update -n base -c defaults cond

As claimed in https://github.com/conda/conda/issues/8954, some issues related to conda are fixed.