Office.js Not Fully Loaded Despite Calling Office.onReady()

Question

When developing a Word add-in, the following error message is encountered: "Office.js has not fully loaded. Your app must call 'Office.onReady()' as part of its loading sequence (or set the 'Office.initialize' function). If your app has this functionality, try reloading this page."

The implementation of Office.onReady is as follows:

Office.onReady((info) => {
  if (info.host === Office.HostType.Word) {
    document.getElementById("sideload-msg").style.display = "none";
    document.getElementById("app-body").style.display = "flex";
    document.getElementById("run").onclick = run;
  }
});

Attempts to set the Office.initialize function have also been made, but the issue persists. Is there a known solution to this problem?