The “download trial” link gives me a 404 error. On all 3 browsers.
Try this link: https://www.avast.com/download-software
What link were you using? (You didn’t say)
https://www.avast.com/secureline-vpn#pc
This one is working without a problem for me.
I used the link on the product page. It went to the download page, but then redirected to the 404 page. I tried the same link today and it worked. The file http://secureline.tools.avast.com/tools/secureline/avast_secureline_setup.exe was unavailable yesterday (per the 404 page).
Try to imagine how long a cable is between your home and the avast server and how many hardware there is involved.
A glitch somewhere can always happen.