Pretty sure it is because they released a new version that requires IOS 10 and higher. I think the data stream changed and the old app doesn't know what to do with it. I have an iPod Touch 5th gen only 2 and half years old - still works great. I uninstalled the LDS Tools and when I went to reinstall it I got the message there was a new version I couldn't install and would I like the old one? My wife's iPhone 6 works and her iPad2 does not. So it looks like anything with A5 chip is no longer supported (last available IOS is 9.3.5).
Sure hope they change their minds and release a 9.3.5 compatible update as the hardware is viable - just no Apple support.
Also in the first post "PLEASE READ before posting in this section" the link to
https://tech.lds.org/wiki/LDS_Tools_for ... own_Issues only shows issues up to version 2.0.