Update at first to 1.0.4
From 1.0.4 I just updated, so I know that it works. But be aware of old plugins, most of them doesnt work under php 7
- use files Update from 1.x to 2.0
- you will get info about files that need to be deleted - delete them (it will be twice - automatical delete and manual delete)
- update system (message Add new or missing core settings)
- if everything works, do Update from 2.1.4 to 2.1.5
- do the update of plugins banners and download
If you get white page - switch to bootstrap3 theme and unistall (without deleting data) plugins marked as no compatible with version 2 (or better let there only compatible plugins).
Then find the reason of white page.