Why is the code font not working on Firefox while it is on Chrome?

(defun stand-minutes ()
  "Stand minutes"
  (interactive)
  (let* (
         (todays-date (format-time-string "%Y-%m-%d"))
         (minutes-file "~/.config/emacs/minutes.txt"))
    (if (file-exists-p minutes-file)
        (progn
          (with-temp-buffer
            (insert-file-contents-literally minutes-file)
            (setq first-line (buffer-substring-no-properties
                        (line-beginning-position)
                        (line-end-position)))
            (unless (string= first-line todays-date)
              (find-file minutes-file)
              (erase-buffer)
              (insert todays-date "\n" "0")
              (save-buffer)
              (kill-buffer)
              (message "Updated minutes.txt to current date"))))
      (progn
        (find-file minutes-file)
        (insert todays-date "\n" "0")
        (save-buffer)
        (kill-buffer)
        (message "Created minutes.txt")))))

(stand-minutes)

Firefox: https://i.horizon.pics/2WXggwzowP.png
Firefox Developer Edition: https://i.horizon.pics/XkAkrmBNlA.png
Chromium: https://i.horizon.pics/A6zyJXswiK.png