Struggling to Install Mason/lspconfig.

[itswptom]

I'm not new to Vim/Neovim, but I'm new to Lua and creating configs with it. I'm trying to install Mason and the associated lsp-config but keep getting an error that Mason is not found. I believe I've done everything right, but would appreciate knowing if I've missed something. Within my nvim/lua/user/plugins/lazy.lua file, I add the following:

    'williamboman/mason.nvim',
    'williamboman/mason-lspconfig.nvim',
    'neovim/nvim-lspconfig',

Within the nvim/lua/user/plugins/lsp.lua file I add:

require('mason').setup({
    ui = {
        icons = {
            package_installed = "✓",
            package_pending = "➜",
            package_uninstalled = "✗"
        }
    }
})

require('mason-lspconfig').setup({
    -- A list of servers to automatically install if they're not already installed
    -- ensure_installed = { 'pylsp', 'cssls', 'lua_ls', 'dockerls', 'eslint', 'gradle_ls', 'html', 'htmx', 'jsonls', 'java_language_server', 'tsserver', 'jinja_lsp', 'kotlin_language_server', 'markdown_oxide', 'intelephense', 'sqlls', 'somesass_ls', 'vimls', 'lemminx' },
    ensure_installed = { 'pylsp' },
})

-- Set different settings for different languages' LSP
-- LSP list: https://github.com/neovim/nvim-lspconfig/blob/master/doc/server_configurations.md
-- How to use setup({}): https://github.com/neovim/nvim-lspconfig/wiki/Understanding-setup-%7B%7D
--     - the settings table is sent to the LSP
--     - on_attach: a lua callback function to run after LSP attaches to a given buffer
local lspconfig = require('lspconfig')

-- Customized on_attach function
-- See `:help vim.diagnostic.*` for documentation on any of the below functions
local opts = { noremap = true, silent = true }
vim.keymap.set('n', '<space>e', vim.diagnostic.open_float, opts)
vim.keymap.set('n', '[d', vim.diagnostic.goto_prev, opts)
vim.keymap.set('n', ']d', vim.diagnostic.goto_next, opts)
vim.keymap.set('n', '<space>q', vim.diagnostic.setloclist, opts)

-- Use an on_attach function to only map the following keys
-- after the language server attaches to the current buffer
local on_attach = function(client, bufnr)
    -- Enable completion triggered by <c-x><c-o>
    vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc')

    -- See `:help vim.lsp.*` for documentation on any of the below functions
    local bufopts = { noremap = true, silent = true, buffer = bufnr }
    vim.keymap.set('n', 'gD', vim.lsp.buf.declaration, bufopts)
    vim.keymap.set('n', 'gd', vim.lsp.buf.definition, bufopts)
    vim.keymap.set('n', 'K', vim.lsp.buf.hover, bufopts)
    vim.keymap.set('n', 'gi', vim.lsp.buf.implementation, bufopts)
    vim.keymap.set('n', '<C-k>', vim.lsp.buf.signature_help, bufopts)
    vim.keymap.set('n', '<space>wa', vim.lsp.buf.add_workspace_folder, bufopts)
    vim.keymap.set('n', '<space>wr', vim.lsp.buf.remove_workspace_folder, bufopts)
    vim.keymap.set('n', '<space>wl', function()
        print(vim.inspect(vim.lsp.buf.list_workspace_folders()))
    end, bufopts)
    vim.keymap.set('n', '<space>D', vim.lsp.buf.type_definition, bufopts)
    vim.keymap.set('n', '<space>rn', vim.lsp.buf.rename, bufopts)
    vim.keymap.set('n', '<space>ca', vim.lsp.buf.code_action, bufopts)
    vim.keymap.set('n', 'gr', vim.lsp.buf.references, bufopts)
    vim.keymap.set("n", "<space>f", function()
        vim.lsp.buf.format({ async = true })
    end, bufopts)
end

-- Configure each language
-- How to add LSP for a specific language?
-- 1. use `:Mason` to install corresponding LSP
-- 2. add configuration below
lspconfig.pylsp.setup({
	on_attach = on_attach,
})

In my nvim/lua/user/init.lua file I am calling both files:

require("user.plugins.lsp")
require("user.plugins.lazy")

What essential step have I missed here?