Unfortunately this rarely works from the IP address ranges Peertube instances on a VPS in a datacenter use. They need to set up a proxy for Youtube sync and use a residential IP address or something that's not blocked by Youtube.
If sync doesn't work for you, check this.
I think after initial installation, you open a browser with the post-installation step and configure a username and password there. I'm not entirely sure, it's been some time since I did it. But depending on installation method, I don't think it has a provided password.
General password advice: Check caps lock, and if you use like a German keyboard if 'z' and 'y' are swapped.