If you are trying to use 4gb or larger capacity card, they are by design, not compatible with your camera. The Kodak Z650 , made in 2005 / 2006, can use cards up to a 1GB capacity. The larger cards have a different file structure.and will not function correctly with cameras made before 2007. A 1GB card is the highest capacity that this camera can use. See page 57 of the manual page attached. 2gb SD cards will work but I have found them to be fairly unreliable in these older cameras. You can get a 1gb card at the link below.
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