Trying to re download from my cakewalk account but I get a message saying

Sorry, but this download key does not appear to be valid for you.

and I'm unable to download the products i paid for

I have emailed customer support without any answer.

Another issue is that I bought software from toontrack and every time I use a ad hoc internet connection the license is no longer valid and i have to download another one because apparently my computer id changes. they only allow you 3 changes before you have to email them to request more codes. I paid over £100 for this and all they can say is they are aware of the problem and plan to look at it eventually

As I remember the download is only valid for a couple of hours.

You need to request another fresh download code, should be easy to do:

There is no information about that at all on their page.

I had this too and eventually got an email from their technical support literally weeks later.

When you log into your Cakewalk account, do you see a table with the headline:

My Registered Products

The table is supposed to have the following columns:

Date / Product / Serial Number / RegCode / Download Link

Clicking on download link for the given product, should bring you to a page where you can download your product.