If condition is not working in rdlc report expression

=IIf(UCase(Fields!Status_PurchHeader.Value)="RELEASED",TRUE,FALSE)

I'm using this, in the visibility expression of Image. Status_PurchHeader either return Open or Released but it's not working. It's not showing or hiding images based on this expression. Is there any problem with my statement?

Status_PurchHeader is the option/Enum field. Open, Released and Pending Approval are its members.

Image of XML code as well as Report Builder