Your ID3 tag header data is over 1/2MB in size. Try using a smaller poster art image in your media. If you convert your image to a jpg alone it will be much smaller with the same picture quality. There's no need to use the itunes 1400 x 1400 image inside your mp3, 600x600 or 300x300 is fine for your ID3 artwork.
The smaller you make this image and your id3 headers, the faster the media will play when played back on the web. The streaming will have to download the first 1MB of your media file before it gets to the actual audio.
You can continue to ues the large image in your media, just keep in mind PowerPress only downloads the first 1/2 MB of the file to detect duration, and if your ID3 tags exceed that 1/2MB then we can't detect it obvioulsy.
You can search this forum for instructions how to increase this download size, if you are comfortable editing your wp-config.php.