Watch model: A2985 Watch system: 10.4（21T216）
Settings > Privacy can not find Developer Mode in Watch OS 10.4. xcode Recent device can not find this watch device.How do I turn on developer mode in Watch OS 10.4。Watch OS 9.5 can find and open it，but Watch OS 10.4 can not find。
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Settings > Privacy & Security > scroll to the bottom and you should see "Developer Mode".
Make sure that you’ve connected the watch’s paired phone to Xcode, and that you’ve accepted any trust prompts on the phone and watch before looking for the Developer Mode switch on the watch.
More information can be found in the following documentation: