Software: Octoprint 0.18.0. (the stable 0.17.0 doesn't work on my pi 4)
Raspberry Pi 4 Model B 2gb.
Inside Putty, I changed the password from "raspberry" to a new one as recommended by PRUSA.
And when I tried to log in with my new password, it says "Access denied".
I tried
I followed this guide to reset it (Googled: How to reset raspberry pi password).
Then this guide (Googled: octoprint reset ssh password).
I even tried to format & reinstall the Octopi image, I guess the password isn't stored there because it didn't work either.
Just can't reset it 
Thanks for the help in advance!
This is good practice.
Just to be clear: we're still talking about logging in via Putty, right?
Are you sure you are accessing the right IP address?
Is caps-lock or num-lock on?
After reinstalling the OctoPi image, the password for the pi user is set to "raspberry". There is no magical other place where a password is stored then on the system partition. So if "it didn't work either", something else is going on. You may be trying to log in on a different device in your network, or your keyboard is having issues.
Turns out that I typed "Pi" and it should be "pi" (username).
oof, I feel like an idiot.
Thank you!
2 Likes