I dont think you are using your active key, because you can't login with that:
This password is bound to your account's active key and can not be used to login to this page. You may use this active key on other more secure pages like the Wallet or Market pages
The active key is requested after you submit the transaction.
You were probably logged in with your master key in the past, because to get the memo private key you need to use steem-python
Hey Miron, thanks for your answer. In fact, because of security reasons, I am usually using my Posting Key. I don't want my Master Key to be leaked to someone who then has complete control over my account. When I am sending transactions, I am prompted to use the Active Key. This was also the case when I tried to send the private message. I then used the Active Key, and still, I got (and still get) this error message.
I have never heard about steem-python. I guess it is only used with bots and apps etc, right?
But you have to use the master password at least once when you create your account :)
You can use steem-python from the command line too, it comes with the command line interface steempy that can create wallets, query transactions, import keys, upvote, tranfer...
One argumemt is updatememokey, ah I a have to get back at it again, maybe when it rains :)
interesting! Love to chat with you about that when we meet in person again. cu!
thx Miron, I have sent my first private message when I participated in the #Neulingschallenge by @TheAustrianGuy quite a while ago. It could be that back then I was using my Master Key. I have never used the "memo private key" before I got this error message. Now I have tried to use it , but still got an error message (see my reply to @luegenbaron).