Media upload from the iphone app just fails. Period. There are some other reports of it and all the advice on how to fix it involves gradually disabling then uninstalling plugins and the full app and I don’t feel like doing that.
But uploads work via browser so my solution will be to pick which images I want to post and to upload those that way and then include them in posts I compose on the phone (because for some reason creating new posts on the browser is interminably slow. At least this will force some advance planning of what I want to post)
In the meantime, have an orangutan.