Download issue

Hi. Ive been using the SSIW app and its been fine for the first 20 lessons and they download straight away. I cant download lesson 21 it says there was a problem downloading the lesson check your network and try again. Ive tried at home and at work, tried 4g, deleted and reinstalled the app and also tried on 2 devices, phone and tablet but still no luck. Can anyone offer any advice or had the same issue. Nick

See here Nick:

App not working on android

Diolch Deborah.