I feel like I must be missing something here.  I logged in with my 'member' account and switched on the notifications for the browser (Chrome for this test) and then in my test subgroup enabled notifications for a hashtag. Then, from my owner account (using Firefox) I sent a message to the test subgroup with the hashtag enabled by my 'member' account.  I receive no notification in the Chrome browser that was still open.  What did I miss?