I use the embed url and token in the same sample and the html loads report without problem.
When apply the html to your reports, ensure both embed url and token are valid.
<html><script type="text/javascript"> window.onload = function () { // client side click to embed a selected report. // handle server side post backs, optimize for reload scenarios // show embedded report if all fields were filled in. var accessTokenElement = document.getElementById('MainContent_accessTokenTextbox'); if(null !== accessTokenElement){ var accessToken = accessTokenElement.value; if ("" !== accessToken) updateEmbedReport(); } }; // The embedded report posts message for errors to parent window. listen and handle as appropriate function receiveMessage(event) { if (event.data) { try { messageData = JSON.parse(event.data); if (messageData.event === "reportPageLoaded") { } } catch (e) { // do something smart } } } var valB = false; // update embed report function updateEmbedReport() { // check if the embed url was selected //var embedUrl = document.getElementById('tb_EmbedURL').value; var embedUrl="https://embedded.powerbi.com/appTokenReportEmbed?reportId=c52af8ab-0468-4165-92af-dc39858d66ad" if ("" === embedUrl) return; // to load a report do the following: // 1: set the url // 2: add a onload handler to submit the auth token iframe = document.getElementById('iFrameEmbedReport'); iframe.src=embedUrl; iframe.onload = postActionLoadReport; } // post the auth token to the iFrame. function postActionLoadReport() { // get the access token. accessToken = document.getElementById('MainContent_accessTokenTextbox').value; // return if no a if ("" === accessToken) return; // construct the push message structure // this structure also supports setting the reportId, groupId, height, and width. // when using a report in a group, you must provide the groupId on the iFrame SRC var m = { action: "loadReport", accessToken: accessToken //oDataFilter: "Table/id eq 'B'", //filterPaneEnabled: "false" }; //var m = { action: "loadReport", accessToken: accessToken }; message = JSON.stringify(m); // push the message. iframe = document.getElementById('iFrameEmbedReport'); iframe.contentWindow.postMessage(message, "*");; } </script><input id="MainContent_accessTokenTextbox" type="hidden" value="eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ2ZXIiOiIwLjIuMCIsIndjbiI6IlBvd2VyQmlBenVyZVNhbXBsZXMiLCJ3aWQiOiJmODFjMTk2Ni1lZGVlLTQxMWItOGY4YS1mODQ0NjAxOWIwNDQiLCJyaWQiOiJjNTJhZjhhYi0wNDY4LTQxNjUtOTJhZi1kYzM5ODU4ZDY2YWQiLCJpc3MiOiJQb3dlckJJU0RLIiwiYXVkIjoiaHR0cHM6Ly9hbmFseXNpcy53aW5kb3dzLm5ldC9wb3dlcmJpL2FwaSIsImV4cCI6MTg5MzQ0ODgwMCwibmJmIjoxNDgxMDM3MTY5fQ.m4SwqmRWA9rJgfl72lEQ_G-Ijpw9Up5YwmBOfXi00YU"><iframe id="iFrameEmbedReport" src="" height="768px" width="1024px" frameborder="1" seamless></iframe><body></body></html>