Simcity buildit building won't upgrade

I have this one building that just won't upgrade to the highest level. It's fully covered by all services and parks I have access to at my level of level 7, it has a smile when I go to the government screen saying it'll upgrade and I've made sure to check it isn't already at max level (it has a population of 900-something where all 7 of my other buildings are 2000+) . Is there something I've missed or is there a hidden cap on how many maxed out building you can have or something?