It is simple to create a new password by clicking the following password recovery link. You will be promted to input your email, and subsequently emailed a link to resst your password. You can also hit the "Forgot Password" link from the login page.
Yes, you can access your certificate of completion anytime by going to your profile (My courses) and clicking the "Certificate" link next to the completed course. You can alco view all certificates in the "Earned certificates" tab.
Many courses have flash components so the first thing to do is make sure you have flash installed. If you are using the Safari Web Browser you will have to download this plugin from Adobe. Chrome should have it by default.
Another thing to try is to access the course via a different browser