You have computed calculation rule for an extension field. But field is not filled with calculated rule.
Reproducing the Issue
Go to Sales work center (as example).
Click on Opportunities.
Open any Opportunity.
You have created calculation rule for extension field abc.
But data is not computed.
Calculation rule works for new instance or document which is getting created newly. For exisiting records, calculation rule will not be filled.
Extension field, Calculation rule, Calculated field, Calculated computation , KBA , calculated field , calculated rule , calculated extension field , BC-DWB-REP-EXT , Extensibility , Problem