Blue Shield of CA refusing to sell health insurance in many zip codes

[Trillo]

3. Citizens are required to purchase insurance or pay a fine.

Blue Shield of California declined an interview with NPR. But in a written statement, the company reported that it’s not selling in certain areas of California because it could not find enough health providers willing to accept a level of payment that would keep premiums low.

There's some interesting asymmetry there. First off, what is the penalty to health insurance corporations for pulling out of markets? Second, what is the penalty to health providers for failing to accept the payments offered?

... the company also is not selling in areas where there is no contracted hospital within 15 miles.

Seems like there are excessive loopholes for insurers. What are the penalties to insurers for failing to sell insurance that correlate to the penalty to citizens for failing to purchase insurance?