[face|come to|hit] (a|the) (brick|) wall

to reach a point where it is unlikely or too difficult to make any progress

The origin of the idiom "a brick wall" can be traced back to the early 20th century. It comes from the analogy of running into or hitting one's head against an actual brick wall, which is immovable and impenetrable. In modern usage, it can refer to any situation where a person or group is facing a significant obstacle or challenge that seems insurmountable.

Despite their best efforts, the researchers hit a brick wall in trying to find a cure for the disease.
The team's efforts to implement a new strategy hit a brick wall due to resistance from key stakeholders.
The company's attempts to enter the competitive market faced a brick wall due to strong competition and market saturation.
The aspiring author faced a brick wall in getting their manuscript published, receiving rejection after rejection from publishers.
The company's expansion plans hit a wall when economic downturns affected the availability of investment capital.