You know who wrote:

They don't work on national rail ticket readers at Victoria and East Croydon
due to a software upgrade being required. This should be in place by the
24th of April.

They don't work at West Croydon, London Bridge and Charing Cross
National Rail either. However, mine worked OK at Marylebone today, so
Chiltern Railways seem to be on the ball.

--
John Ray, London UK.