The first step is identify the problem. After a software update to The iPhone it can not connect to the wifi due to the secuirty protocol the router is utilising.

Second step is possible theory or cause. The router is quite old (2008) and wasw manufactured with the secuirty protocol at the time which was wpa tkip. Apple products are very picky about the secuirty of the wifi it connects to. Thankfully.

Third step is to test the theory. I accessed the routers control panel. I then opened the wifi secuirty panel. I had the option of using tkip, or wpa2 aes, or a combination of the two for compatibility.

Fourth step establish a plan of action and implement solution. I picked the dual mode to avoid compatability issues with older devices that do not support new secuirty standards. This process restarted the router and all devices had to reconnect.

fifth step Verify Full System Functionality and Implement Preventive Measures. After the router was restarted I ensured all devices were able to reconnect to the router. This change of secuirty protocols now allowed iPhones to connect to the router. As the router is quite old it is no longer reciving updates for its secuirty protocols. So it can not use wpa3 aes for example. I notified the owner of the router that upgrading to a new model will be benefivial for device compatibilties and secuirty.

final step document findings. I noted what I had done to fix this issue so I can refer back in case this issue arises again.