Be sure you have chosen a weather station close to your house, and I would recommend tapping on 'More Info' next to the station name to make sure that it looks like it is reporting relatively accurate data.
I picked one about 2.5 miles from my house, and I was supposed to water today, but...the forecast called for .13 inches of precipitation, I didn't bottom out, and the schedule skipped. If it indeed doesn't rain, tomorrow that will be viewed as an observation (vs. forecast) and my system will water. Also, after picking the station, you can look at your graph to see prior observations to see how the station is tracking. This graph is found at app.rach.io --> Zone --> Soil Moisture Level (soon to be in mobile). It shows exact forecast and what flex will probably do (remember, these are predictions, self correcting every day). Note the arrows at the top as it goes out two full weeks.
You can always set a manual one day rain delay until you get the right weather station.
Again, the graph above will show you in detail why/why not a flex schedule will run. My guess, is you have a crop like trees, shrubs, or perennials which have a much larger bucket to fill, but once it is filled it can take some time before you water again. The root zone depth of the crop is the main factor here. Trees are default 24 inches, while cool season grass is 6 inches. So, you can see why it might not water for some time.
If you do have individual questions like above [email@example.com] can take a quick look at your schedule(s) and help you understand why the system is behaving like it is.
Here is much more detailed information regarding the science behind the scheduling
And more flex articles!
Hope this helps.