Conda install -c pyviz holoviz fails

trying to install holoviz the first time following instructions on
https://holoviz.org/installation.html

The “conda install -c pyviz holoviz” step fails with
“ERROR conda.core.link:_execute(700): An error occurred while installing package ‘defaults::rise-5.6.1-py37_1’”

The platform is an ubuntu 18.04