Make sure a compatible SD-card is inserted
into the TX-box. You can use 1GB micro SD and 2GB micro SD for all firmware versions. You can only use 4GB micro SDHC and 8GB micro SDHC for TXMETAWS_E09 and higher firmware. You can find out which firmware you have by going to: Settings -> Diagnostics -> firmware on the top right, on the TX-box webpage.
For more information about the compatibility of an SD-card and the TX-box, please read the corresponding FAQ, which is available
here.