Compiler error: the package not found

[anoureddini]

Salam,
Added the package to .yaml file: jalali_calendar: ^1.0.3
There's no inline error shown (red underline does not show up) but I get a compiler error:

Compiler message:
Error: Could not resolve the package 'persian_date' in                  
'package:persian_date/persian_date.dart'.
lib/services/prayersdata.dart:5:8: Error: Not found: 'package:persian_date/persian_date.dart'
import 'package:persian_date/persian_date.dart';