If that has happened, you may need to resubmit a logo, per http://community.eveonline.com/news/dev-blogs/alliance-logos-you-submissions-re-opened/
If you don't have an alliance logo and want one, please see the above link. It is a wall of text but has CCP's requirements.
If you don't meet the requirements for a logo requirements but previously had one, CCP are apparently allowing some leniency. Age and size of alliance were explicitly called out for previous logo owners.