I installed plesk following this:
And all went well, no errors or anything. I can provide any logs if needed. I'm now on:
On the part for Plesk Onyx 17.8
What I do after I access the https://ip:8443 and enter the ROOT user and server root pw:
- I leave the contact name as Administrator
 - I give my own personal working email
 - I generate a password which i copy into a file for later
 - I click the trial license option
 - Confirm the terms
 - Enter Plesk
 
What happens afterwards is I get a screen with a green bar on the bottom and it says "initializing plesk". After that, by the guide, I should be on a different page, but it just takes me back to the same page where I must type name email and so on.
I have also tried logging in with Administrator and the new password rather than root, but it says invalid credentials. Any ideas why this is happening?