Audio can't be heard on iPhone when in "Silent On" mode

Hi, Shonna! I am happy to help with your first post, and hoping I can. I am also hoping you're well and safe.

To make sure that we are precisely on the same page, there were 3 courses tested using an iPhone 8 Plus. It should make sense that the expectation is for all these 3 to behave in the same manner. Strangely, one course behaves differently. For this, when the iPhone is set on Silent, it has no sound when "Speaker" is the output but has a sound when earbuds are plugged in. I hope my grasp of the issue is correct and please feel free to clarify my understanding.

From this understanding, what's very peculiar is that this one module seems to be behaving correctly while the other two are not. You may refer to this thread elucidated by Ashley, one of Articulate's staff.   

I have some questions to help me isolate further:

• At this point, the issue seems to be pointing more on the irregularity of the 2 files. Were all the 3 courses created during the same sitting? or the two files were made on one day and that one file was finished on another. If Yes, there could be something distinct for each of these days (e.g. software update was performed for one). In this situation, you may try importing all the 3 courses again following these steps to attempt making the file properties common for all. 
• Are you testing all 3 courses using one browser (e.g. Safari) on the iPhone? If yes, can you try another browser or set of browsers (Chrome, Opera, Firefox, etc.) to observe if the behavior will be consistent?
• Is there another iPhone to test your files? There are situations that point to iOS/Android OS irregularities. This can be a noteworthy observation. 

If it is convenient for you to share the files, it will be helpful. Thank you and keep in touch.