What is the ruling of the religion regarding a husband's refusal to treat his wife's vaginismus, which prevents marital relations and conception, and is the wife sinful if she seeks treatment without his knowledge?

A woman has the right to conceive and to seek medical treatment for anything that prevents her from doing so. Her husband does not have the right to prevent her from this unless there is a legitimate Sharia (definition)-compliant reason. He would be sinful if he prevented her without a lawful cause. However, she must obey him if he forbids her from seeking treatment from a male doctor when a qualified female doctor is available. If the husband insists on preventing her without justification, she is permitted to seek treatment without his knowledge, and it is preferable not to inform him about it.