Why is Twitter not accepting my short url that does not contain .co? the url in question is vote4thame.uk, It works in search engines but doesn't display as a link on Twitter.
Seeing as the URL is primarily a redirect URL, you may wish to just post the final link it directs to as it will be shortened by the t.co shortener.
Also I was able to post a .uk url just fine, so it isn't directly correlated to just .uk domains.
Example URL I used: www.nominet.uk
I was also able to post the URL you provided just fine as well, so perhaps Twitter was rejecting your tweet as spam?