Thanks for contacting us. YouTube strips off the leading “PL”, so the shortened URL in TubePress is safe to ignore. Are you seeing an error message of any kind? If you could, would you send us a link to a page demonstrating the issue? Feel free to send the link via a ticket 1 if you do not want to submit it publicly. Thanks; we look forward to resolving this quickly!
For TubePress’s purposes, the PL prefix can safely be ignored (the YouTube Data API doesn’t care if we supply a leading “PL” or not). However, typing it directly into youtube.com may yield different results.
We tested that playlist ID on our end and TubePress had no trouble displaying the gallery. Are you able to provide a link so that we can take a closer look? Having debugging enabled 1 would also be a great help. Thanks!