One in five people who signed up for health insurance under the new health care law failed to pay their premiums on time and therefore did not receive coverage in January, insurance companies and industry experts say. Paying the first month's premium is the final step in completing an enrollment. Under federal rules, people must pay the initial premium to have coverage take effect. In view of the chaotic debut of the federal marketplace and many state exchanges, the White House urged insurers to give people more time, and many agreed to do so. But, insurers said, some people missed even the extended deadlines.