Xbox live sign in error 801540A9

I cant sign up for xbox live an error 801540A9

From another support thread:

"This error code suggests that a child account is having trouble loading family member profiles. You may see this error code in the following format:

801540A9

Sorry, this profile can't connect to Xbox LIVE on this console. To fix it, download it again.

Solution

Re-associate the child account to the parent account. To do so:

1. Sign in to your Microsoft account and select the
   Family tab.
2. Select Add a child.
3. Enter the email address of the child account that you want to re-associate with the parent account. This will send an invitation to the child account’s email address.
   
4. Sign out of your Microsoft account and sign in to the child account.
   
   Note For security reasons, you may be asked to verify the account.
   
5. Select the button labeled Sign in and accept.
   
   Note Email can be found by selecting View inbox."

Using an xbox one x to play an xbox 360 game

have you tried rebooting the xbox and signing in again?

Hi junim,

Thanks for your post. I understand you are experiencing an issue with logging into your Xbox 360 profile and receiving the error code:
801540A9. Check out this page for steps on how to troubleshoot this issue: Error 801540A9.

Please keep us updated.

Hello, i advise you to check this link Error 801540A9 occurs when you start a game on Xbox One | Xbox Support to resolve your issue.