iPhone 7 (15.8.3) won't connect to iTunes (12.8.3.1)

Just got a second hand iphone 7 to replace my broken iP7 and everything seems to be working correctly with it except every time I try to connect it to iTunes on my mid-2012 Macbook Pro (High Sierra 10.13.6) it says that a software update is required and has the option to install which always fails due to a "problem with the network". But iTunes still connects fine with the old iP7 that is running ios 14.6. I've tried restarting both devices and iTunes multiple times. Can't really think of anything else to do other than maybe downgrading the ios on my new phone. Any suggestions would be appreciated