slump in (someone's) career

Translations
спад в (чьей-то) карьере
After several years of success, he experienced a slump in his career.
После нескольких лет успеха он испытал спад в карьере.
Definitions
A period during which someone's career experiences a decline or setback, often characterized by reduced success, fewer opportunities, or a lack of progress compared to previous achievements.