I would like to upgrade my subscription to have 5 devices protected instead of 3, that I have now. I cannot find anywhere the upgrade button ( that is described at the support page)
There is no Upgrade button to do what you want. The button your are referring to from the support page is a bit of a hold over from when users were still on the older Norton Internet Security, NIS, product. The Upgrade button would upgrade your NIS to the newer 360 product.
How long do you have left on your current subscription. If it is about to expire, you can be sure you have turned off the Automatic Renewal for the current subscription and then purchase the new subscription for the number of devices you wish to cover.
If you still have a long time to expiry, you can contact Norton Support and ask them to help with the change of subscription levels. www.norton.com/contactcs If using the chat option, as soon as you get to enter any information, enter "agent please" to get out of the chat bot and connected to a human.
Hi, Twitte2017. Yes, you can. Contact Norton Support. http://norton.com/chat
They can help with subscription issues.
You can purchase the new product, and should ask Support to add the remaining days from your current subscription to your new one.