Most Tube station ticket machines are only accepting bank cards. You can top up using your contactless and Oyster account, the TfL Oyster and contactless app or an Oyster ticket stop. Ticket machines at all London Overground and DLR stations are still accepting cash.
London Overground: No service Highbury & Islington to Clapham Junction / New Cross / West Croydon / Crystal Palace and Liverpool street to Enfield Town / Cheshunt (via Seven Sisters) / Chingford due to planned engineering work. A reduced service is operating on all other London Overground lines due to operational restrictions.