For better success I Trim my EE links to the root of the forum
In links I will put just
The EE script do this, but is more safe this way.
Also keep in mind that not all EE allows signatures/Bios link
The page not found, I got them a lot when I scrape urls, many sites have moved to other platform or just don't exist anymore.
About no links. Please verify if you are using advanced links or normal and if you have the fields filled. EE script do this link > [your About me] [url with title] + ... (more links if advanced)
Does the SickSubmitter scripts with EE work well?