This is the info I have about growing thyme - never had a problem growing it myself.
thyme is one of those herbs which need a poor quality subsoil mixed with grit (sharp sand ) with good drainage and full sunlight. No feed required. Only water in the summer. In winter let them become thoroughly bone dry. Cover (or bring inside) in winter to prevent the roots getting too wet & cold.
Thyme mustn’t be shaded by objects or other plants (even itself) otherwise it will go woody. Keep cutting back even if produces more than you use to ensure new tender growth.