These like full sun and well drained soil, but when first planted, will need watering regularly and thoroughly till they put out new roots for themselves. I don't know what part of the country you live in, you haven't said, unfortunately, so can't guess at what your local weather conditions have been like recently - drought will have had an impact, as would cold.

There's a full page about Tamarind growing on;
http://www.backyardgardener.com/plantname/pda_5286.html