When I check my settings, it looks like everyone in my group should be getting emails, but then in users, it appears that not all users are being sent email updates (eg. last email 5 months ago) - and those people do not have email settings changed to prevent email summaries. Even I have not received an email summary and I have not changed my email settings. However, the test email to myself did work.
You could check the email logs for more clues? Is there anything under skipped? Filtering by ‘digest’ for sent and skipped may help narrow it down. If you can pin down if they’re being generated at all that may help find the cause.
If you still have the default default email digest frequency as a week, and the default suppress digest email after days as 180 days, then a summary email should be generated for anyone who hasn’t seen the forum in between those times.