AppleJr is an iOS guide website for IPA installation, ESign, Scarlet, KSign, DNS profile, and sideloading tutorials.
Yes, you can use iOS signing apps such as ESign, Scarlet, or KSign.
This usually happens when the developer profile, certificate, or app verification is not working properly.
This can happen because of revoked certificates, blocked installation, unsupported iOS version, or a broken IPA file.
The official website is: