swift - observeSingleEvent is not triggering -

my observesingleevent not being triggered. set breakpoint @ let annotationref.. , goes through that, annotationref.observesingle.. , skips right on block of code under end of method. issue?

let annotationref = database.database().reference(withpath: "annotationitems")                       annotationref.observesingleevent(of: .value, with: { snapshot in       // not print     print("it works")   }) 

i have checked related questions. other things i've tried (and still didn't work):

1) turn off disk persistence

2) let newref = database.database().child("annotationitems) newref.observesingleevent(of: .value, { snapshot in

3) observe vs. observesingleevent

4) added listener

this database structure

"annotationitems" : {      "apple infinite loop" : {          "city" : "cupertino",      } }