What should I do if an "IPA package decompression error" occurs when using 3utools to sign the IPA package? 

As seen in the image below:

Solution:

1. The IPA package is damaged. (If the IPA package is damaged, you can re-download the IPA package, but if there is a problem with the internal files of the IPA package, there is no way)

2. The IPA package is monitored by antivirus software. (If the IPA package is monitored by antivirus software, you can exit the antivirus software and try again)