In this update, we did an overhaul of the codes to support the newer framework. At the same time fixed a few bugs which includes the failure in conversion from PNG and JPEG to PDF and fixes an issue where the Preview images are not showing up in PDF Optimizer.
If you have registered the app in the past, it may show up as expired in this update. All you need to do is to reapply the license file and it should do the trick. If you do not have your license file, do drop us an email at email@example.com and we will be glad to send it to you.