[help] Vim-plug canot be loaded

I get this when set up the vim plugin :
```
line 15:
E117: Unknown function: plugin#begin
line 16:
E492: Not an editor command: Plug 'vim-airline/vim-airline'
line 17:
E117: Unknown function: plugin#end
Press ENTER or type command to continue
```
And the result for :scriptname is this:
```
1: /usr/share/vim/vimrc
2: ~/.vimrc
3: /usr/share/vim/vim82/filetype.vim
4: /usr/share/vim/vim82/ftplugin.vim
5: /usr/share/vim/vim82/indent.vim
6: /usr/share/vim/vim82/syntax/syntax.vim
7: /usr/share/vim/vim82/syntax/synload.vim
8: /usr/share/vim/vim82/syntax/syncolor.vim
9: /usr/share/vim/vim82/plugin/getscriptPlugin.vim
10: /usr/share/vim/vim82/plugin/gzip.vim
11: /usr/share/vim/vim82/plugin/logiPat.vim
12: /usr/share/vim/vim82/plugin/manpager.vim
13: /usr/share/vim/vim82/plugin/matchparen.vim
14: /usr/share/vim/vim82/plugin/netrwPlugin.vim
15: /usr/share/vim/vim82/plugin/rrhelper.vim
16: /usr/share/vim/vim82/plugin/spellfile.vim
17: /usr/share/vim/vim82/plugin/tarPlugin.vim
18: /usr/share/vim/vim82/plugin/tohtml.vim
19: /usr/share/vim/vim82/plugin/vimballPlugin.vim
20: /usr/share/vim/vim82/plugin/zipPlugin.vim
```

It seems that the vim-plugin is not loaded at all. I apply `chmod 777` to both .vim and .vim/autoload folder. Do we have any suggestions to manually load the plugin?

Thanks!
------------------------------

```
VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Feb 12 2022 04:26:50)
```

- Type:
- [ ] Bug
- [ ] Enhancement
- [ ] Feature Request
- [X] Question
- OS:
- [ ] All/Other
- [ ] Linux
- [X] OS X
- [ ] Windows
- Vim:
- [X] Terminal Vim
- [ ] GVim
- [ ] Neovim