As he was trying to sign up for health insurance through Kentucky’s new online exchange this month, Kenny Wheeler hit a wall.

Mr. Wheeler, an independent sales representative with a neuromuscular disorder, had succeeded where many in other states had failed, getting through a thicket of log-in pages. But when he tried to find out whether two health plans he liked would pay for his medications or let him keep his current doctors, he could not.

He called one doctor on the spot, but the receptionist could not tell him whether the practice was in the new plan networks. Nor could Mr. Wheeler, 61, get quick answers from the insurers themselves. Exasperated, he put off completing his application.

Since the new health insurance exchanges opened for business on Oct. 1, millions of people who have visited the online sites have been unable to enroll because of technical problems and software glitches. But many people who are getting through the log-in process are encountering a different set of problems when they try to determine whether policies sold through the exchanges will provide the doctors, hospitals or drugs they need.

Most of the 15 exchanges run by states and the District of Columbia do not have provider directories or search tools on their Web sites — at least not yet — so customers cannot easily check which doctors and hospitals are included in a particular plan’s network. Most allow customers to search for providers by linking to the insurers’ Web sites, but the information is not always accurate or easy to navigate, health care experts say.

At this stage, even many doctors are uncertain about whether they are contracted with exchange plans from state to state because the plans — and even some of the insurers — are so new. . .