I am not sure what to do, all cards have vanished, but the 'Activity' panel on the board does not suggest anything has been deleted or archived. Eeek
Make sure you don't have any filters turned onĀ https://community.atlassian.com/t5/Trello-articles/Can-t-find-your-Trello-cards-Try-these-troubleshooting-tips/ba-p/2947608
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