If it were me and I had downloaded firmware for the s7-1200 in the past without problems, I would logout, close the browser, open browser, visit this support site, login, and attempt the download after searching for it instead of going straight to the download link.   It might be the download link has been updated but your browser cached it to help you and the support site has not notified your browser that page has been superseded.

If that does not work, use a different browser, login, search for file, download file.

I use the industry mall with the PLC part # and search for support documentation and downloads, then restrict it to just downloads, and add "firmware" to the search terms.

Jihosaft

Hello....

I have registered account....I downloaded FW many times.....and I m logged in.....these time it does not work.....

Thanks