Using Finder (macOS 10.15 and later) or iTunes File Sharing (macOS 10.14 and earlier) it is possible to manually transfer your LogTen Pro data file from your iOS device to your computer.
From Finder or iTunes, copy the LogTenProData folder to your computer. This folder contains both your logbook data and your images and signatures.
For complete Finder File Sharing instructions see this Apple article: https://support.apple.com/en-us/HT210598
For complete iTunes File Sharing instructions see this Apple article: https://support.apple.com/en-us/HT201301.