SSRS 2012 Conditional Formatting Color Issues When Exporting to Excel

Hi all,

We recently upgraded to SQL 2012 from SQL2008 R2. I'm having a strange issue with SSRS2012.

One of the report has conditional formattings on cell background colors. Everything works fine when render the report in browser or preview mode. However, the conditional formatting stop working when export the report to Excel (no issues if export to pdf). All cells are high-lightened with pre-defined color although it should only high-lighten those cells that fulfil the condition.

Has someone encountered this issue before ? Thanks for any help.