"ctml"#p173024 Thanks very much!
I am not sure if this could be because of Folder Ownership? In the installation page, it mentions that "During installation, Flarum may request that you make certain directories writable. " During installation, Flarum didn't request folder ownership, and I just did the following.
$ chmod 775 /Applications/MAMP/htdocs/flarum
$chmod 775 -R /Applications/MAMP/htdocs/flarum
and the result it:
chmod: -R: No such file or directory
Thanks again for taking time to help me!