You are trying to export the Intrastat declarations in excel format but the Export button is grayed out.
Reproducing the Issue
1. Go to Intrastat work centre.
2. Go to Intrastat Declaration view.
3. In Show Enter All Intrastat Declarations.
4. Select the Intrastat ID.
5. Select the Edit button.
6. Navigate to the Items tab.
7. We can see the Export Button Disabled.
The Intrastat declarations that are in status Released will only have the option of Export to Excel at the items tab . The Intrastat declarations that are in status In Preparation or Release cancel will not have the option of export to excel for items.
This is standard system behavior.
KBA , SRD-SRM-GLO-INT , UI Intrastat & Foreign Trade Product Classification , How To