Readability have gone out of business, so unfortunately URLs run through their service will no longer work correctly.
Go to Settings and then Tweets, then scroll down to "URL Action" and make sure something other than "Open With Readability" is set.
If you are opening a link and still seeing readability with that option turned off, if there is a chair icon on the top of the screen for that link, tap the icon to turn off readability for that particular link. Readability should then be defaulted to off in both cases.
Sorry for the inconvenience. We are working on getting Readability removed and looking into potential replacements for a future release.