Installing the iOS 12

ok so I have an iPhone 6s+ and an iPad mini which are both able to download and install the new iOS 12 but every time I try to update them after have already downloaded when I go to instal it it says an error has occurre. I googled why it was doing it and I tryed everything. I made extra space then it needed in my phone I reset it i even tried to undownload it and re download it again but it still says that is has an error the same with my iPad minI. Is there anything else I can do?