I have the same problem. My Omron blood pressure unit still reliably transfers its data to the Omron Connect app. Inside the Apple Health app, I can see Omron Connect is a source and it has all read and write permissions. From the Health app, under data sources, I can see all the blood pressure measurements are there.
However, the Health app says that I don't have any blood pressure measurements from the last four months. That is incorrect.
Also, from inside the Health app, it shows the Omron App as being "Inactive". From inside the Omron App, it says that it is connected to the Apple Health App.
Something isn't handshaking between these two apps (Apple Health and Omron Connect) and I've tried everything I can find on the iPhone settings and inside both apps. No solution. I called Omron support, they were of no help at all.