Can you describe how low the volume is? Any other headphones or earphones to compare to and their volume percentage? Hard to understand what you define as low volume.
I suppose you have charged your earphones all the way up? One article on the B&O support page for another pair of Beoplay headphones suggest that battery level might impact the volume, but it's more of a sudden drop in it. With speakers it might be caused by overheating.
I was wondering if it exchanging it for another pair would give you a better idea. Otherwise it must be a software fix if the eartips make no difference or the way you put them in. I wonder if others have reported the same issue...