After contacting support, they asked me to check in the "Alerts" window in TWS if I had an alert set. There wasn't an alert there for trades/fills. However, I never originally created any alert (that I know of) to get email notifications for trades/fills. It was kind of just set up that way and worked automatically for years. I never had a reason to open the "Alerts" window in TWS, so I don't know if there "used to be" an alert there for fills which was somehow now removed? Or if there was a separate setting for this somewhere on IB's website. In any case, I added a new alert for myself manually, into the TWS "Alerts" window. I guess I'll find out if it works the next time one of my orders fills...