I am trying to ask a question on MS Community.

Microsoft Q&A and other Microsoft communities do not require a personal PIN code to post questions. The “PIN” mentioned in Microsoft support content is related to specific scenarios, such as:

• Windows sign-in PIN for a device
• Product key/PIN for activating Office 2021 on certain new devices in Japan (error code PIN-INAPP-INVALIDPIN-8)

If the site is asking for a PIN in the context of Office 2021 activation (for example, on a new device purchased in Japan after December 2021), do the following:

1. Enter the same Office 2021 product key/PIN again, as the earlier activation issue has been fixed.
2. If the error persists (for example, PIN-INAPP-INVALIDPIN-8), contact Microsoft Support and have the purchase certificate and key card ready. Use the “Contact Microsoft Support” entry point from the article and follow the prompts to reach support.

If the PIN prompt is for something else (for example, device sign-in PIN or account verification), use the normal account recovery or sign-in help flows for that product, then return to the community site after successfully signing in.

References:

• Error code: PIN-INAPP-INVALIDPIN-8 when you try to activate your Office 2021 product key
• Ask a question on Microsoft Q&A