When a living entity falls down to the material world he has to accept a material body, and therefore, in his material embodiment, he cannot be called acyuta

Expressions researched:
"When a living entity falls down to the material world, however, he has to accept a material body, and therefore, in his material embodiment, he cannot be called acyuta"

Srimad-Bhagavatam

SB Canto 4

Because the Supreme Personality of Godhead is all-spiritual, He can descend from the spiritual sky without changing His body, and thus He is known as acyuta, or infallible. When a living entity falls down to the material world, however, he has to accept a material body, and therefore, in his material embodiment, he cannot be called acyuta. Because he falls down from his real engagement in the service of the Lord, the living entity gets a material body to suffer or try to enjoy in the miserable material conditions of life.

SB 4.20.37, Translation and Purport

The infallible Supreme Personality of Godhead, having captivated the minds of the King and the priests who were present, returned to His abode in the spiritual sky.

Because the Supreme Personality of Godhead is all-spiritual, He can descend from the spiritual sky without changing His body, and thus He is known as acyuta, or infallible. When a living entity falls down to the material world, however, he has to accept a material body, and therefore, in his material embodiment, he cannot be called acyuta. Because he falls down from his real engagement in the service of the Lord, the living entity gets a material body to suffer or try to enjoy in the miserable material conditions of life. Therefore the fallen living entity is cyuta, whereas the Lord is called acyuta. The Lord was attractive for everyone—not only the King but also the priestly order, who were very much addicted to the performance of Vedic rituals. Because the Lord is all-attractive, He is called Kṛṣṇa, or "one who attracts everyone." The Lord appeared in the sacrificial arena of Mahārāja Pṛthu as Kṣīrodakaśāyī Viṣṇu, who is a plenary expansion of Lord Kṛṣṇa. He is the second incarnation from Kāraṇodakaśāyī Viṣṇu, who is the origin of material creation and who expands as Garbhodakaśāyī Viṣṇu, who then enters into each and every universe. Kṣīrodakaśāyī Viṣṇu is one of the puruṣas who control the material modes of nature.