The component you're using is a commercial product. It sounds like you're using their "free" community edition, which is:
Quote:... limited to 5 sheets per workbook and 200 rows per sheet.
The page seems to suggest that this limit doesn't exist in v7.8 or higher, but I'm not entirely convinced that I've read that correctly.
If the latest "free" version still has the limit, then you'll either need to buy the commercial version, or use one of the many truly free and unlimited alternatives. For example:
As I suggested back in February