Why 5g not working in iphone 12 . When will be it fixed.

The following was provided by Apple for the iPhone 12 models:

Data plan required. 5G, Gigabit LTE, VoLTE, and Wi-Fi calling are available in select markets and through select carriers. Speeds are based on theoretical throughput and vary based on site conditions and carrier. For details on 5G and LTE support, contact your carrier and see apple.com/iphone/cellular.

It won’t be fixed because it isn’t broken. 5G is not yet available everywhere, and its range is shorter than LTE/4G. And you also need a 5G SIM, so if you switched a SIM from your old phone you won’t get 5G.

Contact your carrier and ask them if 5G is available from them and if your plan is ok.

Regards

Giulio