Hello Pauline Chow,
Thank you for your contribution to the Microsoft community. Just a reminder, here on community we are not able to double check accounts and subscription codes. What we can do here is provide/guide customers with possible troubleshooting steps for the issue.
To apply the 3-month Realms pass to your active Minecraft Realms subscription, you can follow these steps:
1. Log in to your Microsoft account at account.microsoft.com/services.
2. Locate the "Minecraft Realms Plus You + 10 Friends Subscription Server 3" subscription and click on it.
3. Click on the "Cancel" button to cancel the Server 3 subscription.
4. Once the Server 3 subscription is cancelled, click on the "Redeem a code" button.
5. Enter the code for the 3-month Realms pass and click on the "Redeem" button.
6. The 3-month Realms pass should now be applied to your active Minecraft Realms subscription.
After redeeming the code, you should see only one active Realms subscription on your Minecraft account. If you have any further questions or concerns, please let me know!
If the following steps didn't work on your account, it would be the best to reach out our dedicated Xbox Live support so that they can guide you on the proper steps to redeem your Minecraft Realms. They have a better view than us here on community since they are able to pull up your account manually.
Please follow the steps below to reach out to our live support team:
1. Please use this link: Contact us | Xbox Support
2. Scroll down and look at the lower left side if you can see the page matches the country/region you are currently located.
3. If not, please select the country/region it is showing and select the correct one among the lists.
4. Make sure to use to check the available contact times of the support.
5. Select the "Contact Us" button
6. Select the drop-down menu options that will match your concern.
7. The next window will provide you with support articles based on your request and we recommend reviewing the relevant articles before selecting the "See contact options" button.
8. On the final window, you will be presented with multiple options. We suggest selecting either the "Chat online" or the "Request a call" options to speak with someone. Be sure to provide as much detail as possible.
9. If you cannot get connected to the support, please use the Virtual Agent and enter this exact phrase, "Talk to an agent".
10. Should you be encountering issues contacting support, you may try InPrivate Window of your browser, other browser, different device/s or connect to different network.
Hope I helped!
YanYannn
Microsoft Community Moderator
