Which shell are you using? the default in macOS is ZSH so make sure the following lines are in your ~/.zshrc file:

if command -v pyenv 1>/dev/null 2>&1; then
eval “$(pyenv init -)”
fi

If you are not ZSH then you will need to add them to the RC file for your shell, for example `.bashrc`.

You could also try running …

eval “$(pyenv init -)”

… which should activate the pyenv managed python for your current session.