This can lead to a difficult and awkward situation in which the teacher feels offended that the his or her efforts went to naught; and the student feels embarrassed that he or she wasn't able to learn as well as other students. Our best teachers understand that all students don't learn in the same way and (so) they try to find different ways to present information. They present is verbally; they present it visibly on a whiteboard on a screen; they use videos; they have students read some information; they have other students explain their thinking; and so on. We use these different strategies to keep the class interesting and to increase student engagement. But we also do this because we know that all students won't learn the same way and we need to find a way to present the content in different ways so that we reach all of our students.
Einstein has been associated with the quote, "I never teach my pupils, I only provide the conditions in which they can learn." I don't know if he really said this, but the statement may be correct. It may be that no teacher can actually MAKE students learn. It may be that the best we can do is to encourage students to learn. We do this by getting to know our students very well and using this knowledge to include into our lessons those aspects that our students will find interesting. If the students are interested than they are more apt to try their best even if the learning is difficult.
Still, even when we understand about different learning styles and the value of good relationships with students, teachers are still faced with some topics that seem to be difficult for many students. Once again we struggle to crack this code of learning. How do teachers help students to understand complex topics? Indeed, this is the art of teaching. Some teachers are better at this than other teachers. In my experience, the teachers who are able to reach the most students are the teachers who learn from their own experiences (including their own failures) and who seek input from other teachers via conversations with colleagues, reading journals and research, and taking courses about learning.
Learning isn't a complete mystery--but it isn't a completely solved mystery either. Current research about how the brain works will help to answer some of our questions. Collaboration with professional teachers helps too. Teaching is rewarding and (at times) frustrating. As we learn more about the process of learning we will have more teachers with greater abilities to address the needs of more and more of our students.