Magento's latest version uses sodium library and current available CLI_IMAGE isn't having the required version installed.
So after searching everywhere about solution, I figured out to rebuild the cli image. I'm not sure what is wrong with their Dockerfile and it kept failing but after lots of debugging I was able to resolve the issue and create the CLI_IMAGE which works with Magento 2.3.2
All you need to do is change the CLI image and it will work for you.
fin config set CLI_IMAGE="amansrivastava/service-cli:7.2"
Let me know if it works for you or doesn't work.