Trans voters are being blocked from registering in the UK
http://www.pinknews.co.uk/2017/05/21/trans-voters-are-being-blocked-from-registering-in-the-uk/
Pink News/By Meka Beresford 05/21/2017
" A number of transgender people have reported being blocked from registering to vote ahead of the UK elections"
So, it's more of a screw up than deliberate attempt to block voters. The article also mentioned there are alternatives available.