Problem

Scope change warning is thrown for Issues when the sprint is started for not having values for 'Estimate' field &  'Remaining' field.

Issues TB-1 and TB-2 do not have a value for the 'Estimate' field. Values entered after the start of the sprint will be treated as scope change.

Issues TB-1 and TB-2 do not have a value for the 'Remaining' field. Values entered after the start of the sprint will be treated as scope change.

Cause

As mentioned in the error the issues do not have values from Estimate & Remaining field populated. These warning can be ignored and primary shown because the board is configured at Boards > Configure > Estimation as below :

Estimation Statistic : Original Time Estimate
Time Tracking : Remaining Estimate and Time Spent (Track time against issues using JIRA's Remaining Estimate and Time Spent fields. The Burndown Chart will be based on these two values.)

Workaround

There are 2 workarounds to this :

1.  At Boards > Configure > Estimation , configure Estimation Statistic : Story Points
2. Set "0" to all the parent issues Original Estimate field by clicking the edit button on the top right of the issues affected.

Resolution

Enter the values for Estimate & Remaining field in the parent issue. ( Subtask only is not applicable )