The SD750 supports only SD/SDHC cards, so if your card is not of either of those types then likely it will not work. Other possibilities are:
If the card is a micro SD card with an adapter, it likely won't work - they don't play well with Canon cameras, use only full size SD cards, and perhaps something a bit smaller, like 32 or 64GB, given the modest 7MP file size of the camera.
Finally, there are lots of counterfeit cards out there, so if it was really cheap, or not from a trustworthy store, it may be a fake.
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
