The term often used to describe a period of time when mankind did not make significant progress is "stagnation" or "stagnant period." This is a period in history when technological, scientific, or societal advancements were limited or virtually non-existent.
It's important to note that history is full of periods of both progress and stagnation, and these phases can vary in length and intensity depending on the specific context being examined. There have been several instances in the past where societies experienced stagnation, but it's challenging to provide a specific duration as it varies depending on the region and time period in question.
For example, some historians may consider certain periods in ancient history, like the Dark Ages in Europe after the fall of the Roman Empire, as times of stagnation. However, even during periods of apparent stagnation, there were often pockets of progress in other parts of the world.
Overall, it's crucial to remember that history is a complex tapestry with different regions and cultures experiencing different levels of progress and stagnation at different times. As such, pinpointing a specific duration for a global period of no progress is challenging and not necessarily accurate.