Error 715-123280 during Office 365 E5 (Microsoft 365 E5) trial sign-up indicates a sign-up or account validation problem that must be handled by Microsoft support or billing systems.

From the available guidance, the recommended paths are:

1. Verify account and billing details
   • Make sure the profile information (name, address, phone, email) and payment method details are complete and valid in the Microsoft account or organization profile.
   • When signing up, ensure the billing address for the payment method matches the bank’s records exactly.
2. Check eligibility and account type
   • Free trials are limited to users who are new to the specific service. If there was a previous subscription of the same type, a free trial might not be available and a pay-as-you-go or paid subscription may be required instead.
   • If the account is in an unmanaged Microsoft Entra directory or is a Microsoft 365 Developer Program account, it may not be allowed to purchase or activate certain paid services. In that case, use a different account or take over the unmanaged directory as described in the Azure sign-up troubleshooting guidance.
3. Browser and session checks
   • Try a different browser or an InPrivate/Incognito session to rule out cached cookies or session issues.
   • Ensure cookies are enabled and not blocked by privacy settings.
4. If the error persists
   • The error message explicitly instructs to contact support. Use the Microsoft support phone channel for billing/subscription issues so they can look up the EventId/TID and error code 715-123280 in back-end systems and complete or correct the trial sign-up.

References:

• Troubleshoot issues when you sign up for a new account in the Azure portal
• You can't complete a purchase in the Office 365 portal
• Try or buy a Microsoft 365 for business subscription
• Customer Insights - Journeys trial FAQ