Hello, I'm Felipe and I'm an independent Community Expert, and I'll do my best to help you.
I'm sorry to hear that you're having trouble resetting your sign-in PIN. Here are some steps you can try to resolve the issue:
Restart your computer and try logging in again with your PIN. Sometimes, a simple restart can fix the problem.
Try resetting your PIN again, but this time, do it from the Microsoft account website. To do this, go to https://account.microsoft.com/profile/signin and sign in with your Microsoft account. From there, click on the "Security" tab and then "Update your PIN." Follow the prompts to reset your PIN.
If you're still having trouble resetting your PIN, you can try creating a new local account on your computer. To do this, go to Settings > Accounts > Family & other users, and click "Add someone else to this PC." From there, follow the prompts to create a new account. Once the account is created, you should be able to log in with a password instead of a PIN.
If none of the above solutions work, you may need to perform a system restore or reset your computer to its factory settings. This will erase all of your personal files and settings, so make sure you back up any important data before doing this.
If none of these solutions work, it may be best to contact Microsoft support directly for further assistance.