I can't link save data to my Nintendo Account

If you are unable to link your Nintendo Account successfully, try the following steps:
Note that wording may differ depending on your device's OS version.

For Android

1. Close all other apps
2. Select Google Chrome as the default browser
3. Clear the browser cache
4. Close all browser tabs
5. Instead of going through the application, confirm whether you can access the following URL using Google Chrome and sign in to your Nintendo Account
   ・Nintendo Account
    If sign-in is successful, try to sign in from the app again
6.  From Google Chrome go to Settings > Site Settings, and apply the following settings
   ・ Third-party cookies: Allow
   ・ JavaScript: Allow
   ・ Pop-ups and redirects: Block
7.  If you are using any of the following network-related apps or software, consider temporarily adjusting their settings
   ・ Security software
   ・ Memory cleaner software
   ・ Content blockers
   ・ VPN apps
8. Go to Device Settings > Network & Internet and turn off Data Saver
9. If security software is installed, disable it temporarily when linking the Nintendo Account
    * You may skip the following steps if the device does not have Developer Options.
10. Go to Developer Options > Apps > Don't Keep Activities and confirm if it has been enabled. If it has, disable it
11. If you have modified the "Background process limit" setting in Developer Options, disable it

For iOS

1. Close all other apps
2. Close all browser tabs
3.  Go to Settings > Apps > Safari > Advanced and disable Block All Cookies
    * You may skip the above if it is already set to Block All Cookies.
4. Go to Settings > Apps > Safari and tap Clear History and Website Data
    * Be aware that clearing this will delete the history, cookies, and other browse data.
5. Go to Settings > Apps > Safari > Advanced and check whether JavaScript is turned on
6. If Private Browsing is turned ON, turn it OFF
7. Instead of going through the application, confirm whether you can access and the following URL using the Safari browser and sign in to your Nintendo Account:
   ・Nintendo Account
    If sign-in is successful, try to sign in from the app again

If the issue persists after trying the above steps, please confirm the following:

1. Go to Settings > Screen Time > Content & Privacy Restrictions > App Store, Media, Web, & Games > Web Content and set as Unrestricted Access or Unrestricted
   * If Content & Privacy Restrictions is turned OFF, keep it as it is.
   * If Web Content is set to Only Approved Websites, you will not be able to sign in to your Nintendo Account.
2. Go to Settings > Face ID & Passcode or Touch ID & Password and turn off Password AutoFill
3.  If you are using any of the following network-related apps or software, consider temporarily adjusting their settings
   ・ Security software
   ・  Content blockers
   ・ VPN apps
4. Go to Settings > Cellular or Mobile Data > Cellular Data Options > Data Mode and select Standard
   * Depending on your OS version, the options above may not be available on your device.