CRM Plugin Message Export,ExportAll,ExportCompressed,ExportCompressedAll fire in plugin

1. Connect to SQL Server where CRM DB is located.
2. Open SQL Management Studio, open new query with context of your CRM DB (CRM_MSCRM or other name).
3. Execute following T-SQL Script:
Update SdkMessageFilter
Set IsCustomProcessingStepAllowed = 1
Where SdkMessageId in (Select distinct SdkMessageId From sdkmessage where name = 'ExportSolution')
4. Make IISReset.

5. Restart plugin registration tool - ExportSolution should be available for handling with plugins.