解决方法（摘自b站https://www.bilibili.com/opus/1130656411342077990）：
此方法多次测试有效
具体操作：
确保后台没有Edge相关进程时，
找到 %LOCALAPPDATA%\Microsoft\Edge\User Data\Local State 文件
修改variations_country 键的值为 "US"，
"variations_country":"CN”时，Copilot按钮不显示，
"variations_country":”US”或其它Copilot支持的国家/地区时，Copilot按钮显示。
将此过程做成powershell脚本，直接复制粘贴到Powershell运行
& {
Get-Process | Where-Object { $_.ProcessName -like "msedge*" } | Stop-Process -Force -ErrorAction SilentlyContinue
$localState = "$env:LOCALAPPDATA\Microsoft\Edge\User Data\Local State"
if (Test-Path $localState) {
$json = Get-Content $localState -Raw | ConvertFrom-Json
$json.variations_country = "US"
$json | ConvertTo-Json -Depth 100 | Set-Content -Path $localState -Encoding UTF8
Write-Host "已将 variations_country 设置为 US。"
} else {
Write-Host "找不到 Local State 文件：$localState"
return
}
Start-Sleep -Seconds 1
Start-Process "msedge.exe"
Write-Host "已重新启动 Microsoft Edge"
}