Check Activision's service status, then sign in with the Activision account that already holds your Modern Warfare progress. If you are registering, use a valid email, display name, password, and region and complete any email verification. Do not unlink a platform account to troubleshoot Login Error 0 because progression is tied to the Activision account.
Open Activision Online Services, select Call of Duty: Modern Warfare and your platform, and read the current status. If an incident is shown, keep the account unchanged and retry after the service is restored.
2
Use the Activision account that owns the progress
On the Activision account page, choose Log In and use the email and password for the account already linked to Modern Warfare. If you normally enter through PlayStation, Xbox, Battle.net, or Steam, choose that platform sign-in option. Confirm that the displayed Activision ID and linked platform are yours.
3
Register only if you do not have an account
From Modern Warfare's account prompt, choose Sign Up. Enter a display name, valid email address, password, and region, accept the required terms, then submit. Use an email you can access because recovery and security messages go there.
4
Complete the verification request
Open the newest Activision message sent to the registration email and follow its verification link if prompted. Return to the game or account page and sign in again. Do not request repeated messages while an earlier verification is still pending.
5
Confirm the platform link without changing it
In the Activision profile, open Account Linking and verify that the platform running Modern Warfare is listed under the intended account. Do not unlink it as a login test: Activision says progression is stored on the Activision account and does not move when a platform link is moved elsewhere.
6
Verify access in Modern Warfare
Close and reopen Modern Warfare, sign in, and wait for the online main menu. Open Social or Account and confirm the expected Activision ID and progression. Reaching that screen with the correct profile confirms the registration or login path worked.
If it does not work
If the password is rejected, use Forgot Password on the Activision login page and complete the reset from the account email. Do not create a second account to bypass recovery.
If no reset email arrives, confirm the address and spam folder. Activision says some accounts created through a platform may require signing in with that linked platform before adding account details.
If the profile shows the wrong progress, stop before linking or unlinking anything and recover the original Activision account.
If Login Error 0 remains while services are operational, record the platform, time, Activision ID without the password, and exact error, then use Activision Support.
ⓘ Sources and verification
Checked against official documentation on . Scope: Windows, PlayStation, Xbox.
Source-checked against Activision's current account-registration and profile-management guidance. No account was created or unlinked during review.
