Noticed that FeatureLayer refreshInterval() -method is broken with ArcgisJS 4.9. With older ArcgisJS 4.8 refreshInterval() is working.
Also noticed that FeatureLayer refresh() -method does not work in ArcgisJS 4.9.
Hopefully this will be fixed in next release.
attached samples, you need to check your developer tools --> network -table that queries are happening in 4.8 but not in 4.9.