I can’t update my iPhone 6s Plus running iOS 15.8.2

Why cant I update my iPhone 6s Plus running ios 15.8.2 I want to update to ios 15.8.3 and I have enough available space and my network is good . I don’t have pc so please any suggestions then please let me know this is biggest problem for me now . When I try to update its show ubal le to check for updates and it’s stuck in loading