Hello kiran potnis
First of all, welcome to the SBB Community.
The Swiss love niceties, for example when people greet before asking a question.
You probably have a Swiss Travel Pass, not a Swiss Pass. You should not confuse the two!
The ticketing system does not know that you own the Swiss Travel Pass.
There is no need to purchase ticket for the Swiss stretch when you have the Swiss Travel Pass. It would have been sufficient to purchase a ticket from the French border to the Chamonix, only.
Alternatively, you could go to your passenger details and select ‘GA Travel Card’. It is the resident’s equivalent of the Swiss Travel Pass.
Kind regards,
Roland