Why did sanctions against North Korea's missile program fail?

Since 2011, under Kim Jong-Un's leadership, North Korea has tested 4 new missiles for the first time

North Korea’s successful test of an intercontinental ballistic missile (ICBM), allegedly with the capability to hit Alaska, is the latest in a series of significant advances for the country’s missile program.

North Korea has been seeking to develop long-range missile technology for over 20 years. For much of this period, the international community has been trying to stop that from happening.

My research on how states illegally obtain missile technologies and my experience conducting outreach related to UN sanctions give me some insight into the methods North Korea used to make illicit procurements