In Surah Isra [17:61] the ayah is as follows:
And (remember) when We said to the angels: “Prostrate unto Adam.” They prostrated except Iblis (Satan). He said: “Shall I prostrate to one whom You created from clay?”
In Surah Kahf [18:50] it reads:
And (remember) when We said to the angels; “Prostrate to Adam.” So they prostrated except Iblis (Satan). He was one of the jinns; he disobeyed the Command of his Lord.
This is an example of something that some Non-Muslims may claim is an incoherency. Why is the same story split up into different places with different details? Good question.
Let’s take a quick step back. We know that Surah Isra is also sometimes called Surah Bani Israa’eel [children of Israel/the Jews]. It also contains a series of ayaat that Ibn Abbas(ra) mentioned were similar to the 10 commandments given to Musa (alayhis Salam) [Surah al An'am 6: 151-153]. So this surah is primarily addressing Bani Isra’eel, who had knowledge but became arrogant.
Surah Kahf is addressing the Christians. We can see this from ayah 18:4, “And to warn those who say, ‘Allah has begotten a son (or offspring or children).’” The Christians disobeyed their Lord.
So when the surah is addressing those who were afflicted with arrogance (i.e. the Jews), the part of the story mentioned is the one pertaining to them [i.e. Iblis did not prostrate to someone Allah ordered him to prostrate to, out of thinking that he is superior. Similarly, the Jews rejected Prophet Muhammad while thinking thinking they are superior].
When the surah is addressing a different audience (i.e. Christians), it uses the part of the story most pertinent to them [i.e. Iblis disobeyed the Command of his Lord, and many Christians disobey their Lord while still thinking their on the right path].
Furthermore, Allah tells us in Surah al Kahf that Iblis was of the Jinn. This clears the doubts of Christians who say that Iblis was a 'fallen angel'.