Hi, I'm on an android phone as well and found a quick way round this, I get it every now and again, usually when I've been logged out due to timeout...
Basically, just use click on the "main site" button to get the error main site desktop view, then use the link at the top right to go back into the android Web view, each time I do that it then shows the Turing Test, allowing me to enter the letters while logging in.
Hope that helps. I must admit I don't find the android web view too bad, certainly a lot better than the desktop view on my phone.
Another tip I found, normally when researching a WG I need to go into the desktop view to get their user id in the text near the bottom of the page, however the same id is in the url of the android Web view and you can quickly copy it from there into UKP to do a search to see if the same profile is reviewed or mentioned.
Might be teaching prossie to suck cock there but someone might find it useful