Understanding the effectiveness of peer mentor training in online learning environments prepares students for their roles as online peer mentors. In the Learning Assistant peer mentor program, Learning Assistants (LAs) play a crucial role in supporting student learning and engagement in STEM courses. Due to the shift to online learning during the COVID-19 pandemic, many LAs began working in online synchronous and asynchronous courses. We gathered information on challenging interactions encountered by LAs, and the frequencies of these interactions were analyzed and compared between the two learning environments. The results revealed that while no new challenging interactions emerged in the online environment, there were nuances in how existing interactions manifested online. In this article, we present new challenging interaction scenarios designed for online learning environments. These scenarios aim to enhance the training in the LA pedagogy course. Furthermore, the study highlights the significance of behavioral engagement barriers, such as unprepared and disinterested students, which had higher frequencies in both in-person and online environments. These findings help create a foundation for online LA training by incorporating new scenarios and focusing on behavioral engagement barriers to help the LA pedagogy course better equip LAs to navigate challenging interactions and support student learning.