Patron could log in and view checked out items using her iPhone, but was prompted to log in indefinitely after attempting to renew or request any items. (iOS 8) Patron reported a similar situation when using her Mac. (iOS X Lion)
I could not reproduce this problem in the bootstrap theme in 3.16.x using an iPhone running iOS 8.1.1. What version of Koha is being used? What OPAC theme?
With no additional information about how to reproduce this problem I will consider this report invalid. Please re-open if you can provide additional details.