A few months ago, when I was posting about problems, I'm pretty sure I got notified by email when someone replied to a post. I no longer get notified, and find it difficult to remember which topic I have an unresolved question in. There is no "subscribe to this topic" below where I'm typing this (as there is in my own forum), just below "check here to include your profile signature". What happened? I find no subscribing places anywhere in the community.
Looks like you don't have Subscriptions enabled. Check the feature configuration page in Admin Options. The My Subscriptions like still shows as before.