Thanks Jon, does that mean I have to pay by the month or year to use it?
The perpetual license version (disks or one time download) stopped at 12.0.3.
If you want something newer than that, yes, you would need to become a creative Cloud Subscriber so you could download and install a more recent version. There is a 7 day trial available, but you only have access to CC 2017.5 with that.
The subscription you choose it up to you. Once you have one, the program(s) will install on your machine, just like the old versions, and can be used on or offline (it's not a Cloud-Based Program). CC needs to call home periodically to ensure you have a valid subscription. If you don't, access to the program stops, though all of the files that you've created are still available to you
Subscribers have access to 8 versions, though only 5 can be installed at once (dot releases overwrite each other), so CS6 Cloud, CC, CC2014.x, CC2015.x and CC2017.x can all be installed on the same machine(s) at the same time, under a single subscription, they just won't run concurrently.
All of that said, there are many users who still have the old CS6 and can still connect to their servers without any issue what-so-ever. Getting a newer version of DW is certainly no guarantee a successful connection will happen. Have you tried toggling "Use Passive FTP" and "FTP Performance Optimization" in the Advanced section of your FTP settings? Sometimes changing one, or both of those will make a difference. I've also had times where DW simply wouldn't connect using the domain address and required me to put my server's IP address in that field in order to connect with it (or vise versa).