Currently stranded in India and being denied a flight home.

For context, when I was at the airport for my flight, the desk agent (Swiss Airlines) told me that they cannot check me in because they can see my booking but it it not linked/confirmed with the airline. After a week of going back and forth with Swiss, United Airlines, and my travel agency every single day, I still am not clear on why I was denied check-in because I don’t know what it means that the booking was not linked/confirmed with the airline.

I have been trying to get somebody to rebook my ticket and finally I was able to pinpoint that Swiss has to rebook me. But they are claiming I did not show up for my flight, which is a blatant lie. They are saying my only option is to pay out of pocket for a one way ticket back to the US.

I have been stuck in India since March 17th and have been given the run around by everybody. What can I do to get back home without paying and is there any legal action I can take against Swiss since none of this was in my control?