Why won't the maintenance workers clean up in zoo tycoon complete collection?

In Zoo Tycoon: Complete Collection, maintenance workers may not clean up because they are either overwhelmed by the amount of waste or their paths are obstructed. Additionally, if there are not enough maintenance workers assigned to the zoo, they may struggle to keep up with the demand. It's also possible that the zoo's layout could hinder their movement, preventing them from reaching certain areas efficiently. To resolve these issues, players can hire more workers and optimize the zoo's design for better access.