Zynex served as a Colorado startup success story — a one-man operation turned public company with hundreds of millions of dollars in revenue. This is the story about how it all fell apart.

When insurance didn’t cover the electrical nerve stimulation device, Zynex promised Houk that she could make 10 payments of $25 to cover the cost. What the Westminster patient didn’t know was that this would kick off a year of fighting with a company determined to bill Houk and her insurance providers as often as possible.

The company billed her old insurance. It billed her new insurance. And it sent her bills for more than $2,000 for the $250 device, when she was already paying it off in installments.

“The billing was relentless and terrifying,” Houk said in an interview.

Houk was one of numerous Coloradans caught up in what federal investigators say was a years-long scheme by Zynex to oversupply medical devices and overbill patients seeking opioid-free pain relief. A federal grand jury indicted two former top executives in January, accusing them of orchestrating the fraudulent practices that netted Zynex nearly $1 billion. The company last month avoided further prosecution by admitting to participating in a conspiracy to commit health care fraud, securities fraud, mail fraud and other violations.