Anonymous Pens can't be embedded.
Edit on CodePen
{"__browser":{"country":"US","device":"unknown_device","mobile":false,"name":"unknown browser","platform":"unknown_platform","version":"0"},"__constants":{},"__CPDATA":{"domain_iframe":"https://cdpn.io","environment":"production","host":"codepen.io","iframe_allow":"accelerometer; ambient-light-sensor; camera; display-capture; encrypted-media; geolocation; gyroscope; microphone; midi; payment; vr; web-share","iframe_sandbox":"allow-forms allow-modals allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-top-navigation-by-user-activation allow-downloads allow-presentation"},"__graphql":{"data":{"data":null,"errors":[{"message":"Cannot return null for non-nullable field Query.sessionUser"}]},"url":"https://codepen.io/graphql","api":"cprails"},"__pay_stripe_public_key":"pk_live_2GndomDfiklqpSNQn8FrGuwZSMIMzha7DkLJqlYe7IR0ihKAlKdiHg68JJc5eVPt68rzAjzAAVXcUwjySHRCsgjQQ00gtRBUFNH","__pay_braintree_env":"production","__boomboom":{"serve_url":"https://cdpn.io/cpe/boomboom","store_url":"https://codepen.io/cpe/boomboom/store"},"__pageType":"embed","__item":"{\"editor_settings\":{\"auto_run\":true,\"auto_save\":true,\"format_on_save\":false,\"indent_with\":\"spaces\",\"tab_size\":2,\"id\":\"VoDkNZ\",\"autocomplete\":false,\"code_folding\":true,\"css_pre_processor\":\"none\",\"css_prefix\":\"neither\",\"css_starter\":\"neither\",\"emmet_active\":true,\"font_size\":14,\"font_type\":\"system\",\"html_pre_processor\":\"none\",\"js_pre_processor\":\"none\",\"key_bindings\":\"normal\",\"line_numbers\":true,\"line_wrapping\":true,\"match_brackets\":true,\"snippets\":{\"markupSnippets\":{},\"stylesheetSnippets\":{}},\"theme\":\"twilight\"},\"hashid\":\"wWomNO\",\"itemType\":\"pen\",\"resources\":[],\"tags\":[],\"id\":8646490,\"user_id\":1,\"html\":\"<div class=\\\"grid\\\">\\n <div class=\\\"flex-1\\\"></div>\\n <div class=\\\"flex-2\\\"></div>\\n</div>\\n\\n<div class=\\\"grid with-gutters\\\">\\n <div class=\\\"flex-1\\\"></div>\\n <div class=\\\"flex-2\\\"></div>\\n <div class=\\\"flex-3\\\"></div>\\n</div>\\n<div class=\\\"grid with-gutters\\\">\\n <div class=\\\"flex-1\\\"></div>\\n <div class=\\\"flex-2\\\"></div>\\n <div class=\\\"flex-1\\\"></div>\\n <div class=\\\"flex-1\\\"></div>\\n <div class=\\\"flex-1\\\"></div>\\n\\n</div>\",\"css\":\"$gutter: 1em;\\n\\n.grid {\\n display: flex;\\n\\n > .flex-1 { flex: 1; }\\n > .flex-2 { flex: 2; }\\n > .flex-3 { flex: 3; }\\n > .flex-4 { flex: 4; }\\n > .flex-5 { flex: 5; }\\n > .flex-6 { flex: 6; }\\n > .flex-7 { flex: 7; }\\n > .flex-8 { flex: 8; }\\n\\n > .align-right {\\n text-align: right;\\n }\\n\\n &.with-gutters {\\n margin-left: -0.5 * $gutter;\\n margin-right: -0.5 * $gutter;\\n\\n > * {\\n margin-left: 0.5 * $gutter;\\n margin-right: 0.5 * $gutter;\\n }\\n }\\n\\n}\\n\\n// This part is not for the grid system so much as it's just here to \\\"see\\\" the grid columns\\n.grid {\\n margin-bottom: 1em;\\n > * {\\n min-height: 2em;\\n background-image: linear-gradient(-40deg, lime, green);\\n }\\n}\",\"js\":\"\",\"html_pre_processor\":\"none\",\"css_pre_processor\":\"scss\",\"js_pre_processor\":\"none\",\"html_classes\":\"\",\"css_starter\":\"neither\",\"js_library\":null,\"created_at\":\"2016-06-22T17:32:40.000Z\",\"updated_at\":\"2016-06-22T17:32:40.000Z\",\"title\":\"Flexbox Grid System\",\"description\":\"\",\"slug_hash\":\"wWomNO\",\"head\":\"\",\"private\":false,\"has_animation\":false,\"team_id\":0,\"css_prefix\":\"neither\",\"template\":false,\"parent_id\":null,\"comments_count\":0,\"custom_screenshot_filename\":null,\"loves_count\":0,\"pick\":false,\"popularity_score\":0,\"views_count\":0,\"pick_visible_at\":\"2022-11-08T22:42:57.485Z\",\"cpid\":null,\"is_new_editor_pen\":false,\"pen_hash\":null}","__processorsMap":{"autoprefixer":"autoprefixer-10","babel":"babel-7","coffeescript":"coffeescript-2","format-1":"format-1","flutter":"flutter-1","haml":"haml-4","less":"less-3","lint-1":"lint-1","livescript":"livescript-1","markdown":"markdown-11","postcss":"postcss-7","pug":"pug-2","sass":"sass-1","scss":"sass-1","sass-ruby-3":"sass-ruby-3","sass-ruby-compass-3":"sass-ruby-compass-3","slim":"slim-3","stylus":"stylus-0","typescript":"typescript-4","vue":"vue-2","vue3":"vue-3"},"__favicon_mask_icon":"https://cpwebassets.codepen.io/assets/favicon/logo-pin-b4b4269c16397ad2f0f7a01bcdf513a1994f4c94b8af2f191c09eb0d601762b1.svg","__favicon_shortcut_icon":"https://cpwebassets.codepen.io/assets/favicon/favicon-aec34940fbc1a6e787974dcd360f2c6b63348d4b1f4e06c77743096d55480f33.ico","__path_to_iframe_console_runner":"https://cpwebassets.codepen.io/assets/editor/iframe/iframeConsoleRunner-6d8bf8b4b479137260842506acbb12717dace0823c023e08b96360e60b0840d9.js","__path_to_iframe_refresh_css":"https://cpwebassets.codepen.io/assets/editor/iframe/iframeRefreshCSS-44fe83e49b63affec96918c9af88c0d80b209a862cf87ac46bc933074b8c557d.js","__path_to_iframe_runtime_errors":"https://cpwebassets.codepen.io/assets/editor/iframe/iframeRuntimeErrors-4f205f2c14e769b448bcf477de2938c681660d5038bc464e3700256713ebe261.js","__path_to_processor_worker":"https://cpwebassets.codepen.io/assets/packs/router.js","__path_to_stop_execution_on_timeout":"https://cpwebassets.codepen.io/assets/common/stopExecutionOnTimeout-2c7831bb44f98c1391d6a4ffda0e1fd302503391ca806e7fcc7b9b87197aec26.js","__pen_normalize_css_url":"https://cdnjs.cloudflare.com/ajax/libs/normalize/5.0.0/normalize.min.css","__pen_prefix_free_url":"https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js","__pen_reset_css_url":"https://cdnjs.cloudflare.com/ajax/libs/meyer-reset/2.0/reset.min.css","__path_to_infinite_loop_detection":"https://cpwebassets.codepen.io/assets/packs/js/infiniteLoopDetection-f0d5935eb4c2121dfc41.js"}