It's an SDHC card, class 10, which defines the read/write speed, although Sandisk put the speed on the card as well. Sandisk are good quality cards, so I don't believe it's a card problem (I use only Sandisk).
The most likely problem, as VHG suggested, is with your card reader. Early SD cards were low capacity and readers were designed to cope with them. As camera sensors increased in size people wanted higher-capacity cards and the SDHC format was introduced. Things progessed even further with camera sensors and the SDHX format appeared. The early readers will not cope with SDHC and SDXC formats and I suspect that your reader might fall into this category. If you can Google your card reader you might find what types of cards it can read.