Why my leader key is not working for y,d,p?

I have some mappings define for "+y, "+p, "+d .. But none of the mappings are working. When I press leader key (,) and then press y or d or p or P, I get beep sound. Can anyone help me why is it not working? Here is my ~/.vimrc content:

 cat ~/.vimrc
call plug#begin()

" List your plugins here
Plug 'elixir-editors/vim-elixir'
Plug 'itchyny/lightline.vim'
Plug 'jaredgorski/spacecamp'

call plug#end()

colorscheme spacecamp

set showcmd
set autowriteall
set laststatus=2
set number
set list
set lcs=trail:.,lead:.

" format elixir files when saving
"augroup filetype_ex
"  autocmd!
"  autocmd BufWritePre *.ex,*.exs execute "!mix format %"
"augroup END

" syntax on
" filetype on
" set clipboard=unnamedplus

let g:mapleader = ","

nnoremap <Leader>w :w<CR>
nnoremap <Leader>q :wq<CR>

vnoremap <Leader>y "+y
vnoremap <Leader>d "+d
nnoremap <Leader>p "+p
nnoremap <Leader>P "+P
vnoremap <Leader>p "+p
vnoremap <Leader>P "+P

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