PuTTY SSH server refused our key
I was having a same problem, I read a few tutorials here in DO and I believe I know what the problem was.
My step was: create a new droplet (brand new account / droplet), not using any key and THEN generate a key after the droplet created.
The problem was, the key was not automatically assigned to the droplet (I read this on one of the tutorials). It is possible to assign the key into an existing droplet (again, read on tutorial) but I didn't use that solution.
My solution: I deleted the key from DO's record, delete the droplet (luckily it was still empty) and then create a new droplet, but this time, using the key since the beginning (when it was asked during droplet's creation, whether we want to use a key or not). Basically just start from scratch, but this time I "rearranged" the steps. I was using the same key, there was a pop up saying that this key already cached but on different droplet (something along that line), hit yes, and everything works.
Just a suggestion, DO should warn the user regarding this issue. Well.. I don't really think that this is an issue / bug, but.. I think it'd be nice to know this since the beginning. For example, on this tutorial:
On this part "Step Seven-Select SSH Keys (Optional)" > It should be clear that it would take more, extra effort if we choose to create a key later (manually assign it to the droplet).