The Association of Zoos and Aquariums has only extended its accreditation for one year.
Normally, the zoo gets five years, if it meets inspection requirements.
Problem is, AZA says Miller Park must get a companion for its sea lion.
Last year her partner died and the zoo has yet to find a replacement.
"We will look for a second sea lion as a companion animal,"said Zoo Superintendent Jay Tetzloff. "That's what we are looking for, and that's what we're working on at this point in time. To see if we can find a second animal."
The zoo says it has enough money to purchase a second sea lion.
It has until next September to make the changes.