What is the login user?
VPS Linux user is root
VPS Windows Server user is Administrator
VPS Windows7 and Windows10 user is Admin

To reset the VPS password
Access to SolusVM Control Panel and reset password at the tab Root/Admin Password

To create your own password
Linux - running this command passwd root
Windows - Maximize Windows and choose one of the followings
1. Press Ctril+Alt+End
2. Press Crtl+Alt+Delete
3. Running this command C:\Windows\explorer.exe shell:::{2559a1f2-21d7-11d4-bdaf-00c04f60b9f0}
4. Access the User Control Panel

Remarks
Under the Manage tab, it accepts a reset the password with an alphanumeric.
After that, you should reset the password inside VPS with the command passwd root and set it up stronger with alphanumeric and special characters