Hi Pragati,
After some further testing I appear to be wrong about the number of rows, it is not 65535 but rather 65530 that is the maximum number of rows for us. I suspect the issue is not tied directly to the number of rows per se, but rather is tied to the number of hyperlinks in the Excel sheet, when that passes 65530 there is an issue (perhaps a 16 bit integer is being used to index the links inside of the save code?)
I have updated the project file to better illustrate this issue. Please run the attached project and once it opens set the number box to 65530, check the box for creating links and press the button. It will take some time (roughly 75 seconds on my machine) to create the file however the file it creates will work properly in Excel. Now turn the number up to 65531 (or higher) and press the button again, the file generated does not open in Excel for me citing the error I posted above.