Hi. I guess you mean Lexar instead of Alexa? Is this a new card you never used before today? If you still have the ,manual of box of the camera you should have the camera model number on them.
The model of card let me think you have a SDHC or SDXC card. Many early camera needed a plain SD card and those usually top at 2G of data. It is usually possible to format a card to be used as a plain SD but sometime it can still have compatibility issue. Try to get hold of a 2G card to test (many don't need them any more, so you can ask around, some store always keep some in store for compatibility reason also but they start to get rare).
SD, SDHC and SDXC all have the same dimention (unless they are of the micro format) so they still fit slot not compatible for them.