Hi-
Exact same thing with me! I understand how to change but absolutely nothing will take effect.
I was changing the files in the bp_template-pack folder but you actually need to change the files (for example the first one in step 3) here:
/wp-content/themes/YOURTHEME/activity/index.php
Took me to reading step 3, 50 times before this was apparent- not sure if this is what was happening to you but this was my problem.. anyways hope that helps…