The Co-op faced an issue with contactless payments at around 200 of its 2,300 stores due to a cyber-attack fallout, affecting deliveries as well.
The problem with contactless payments was fixed by mid-afternoon on Tuesday across all Co-op stores.
Hackers accessed personal data of some Co-op members, but passwords and financial details were not compromised.
M&S and the Co-op both experienced cyber-attacks linked to hacking groups like Scattered Spider and Lapsus$, with investigations ongoing by authorities.