Welcome Wayne,
Thank you for posting in the Microsoft Q&A forum.
To better narrow this down, could you first confirm whether you are signed in to Windows with a personal Microsoft account or a local account? Also, when you open the Widgets board using Win+W, is the Weather widget already added and functioning normally there?
Since other lock screen widgets can be added but only Weather remains unavailable, please try these quick checks:
- Open Settings > Privacy & security > Location and temporarily turn Location services OFF. Restart the PC, then turn it back ON and check whether the Weather widget can be added.
- Open the Widgets board with Win+W, remove the Weather widget if it is already present there, then add it again. After that, return to Settings > Personalization > Lock screen and check the Weather widget status.
- Open Microsoft Store > Library and select Get updates to ensure Windows Web Experience Pack is fully updated, as Widgets features depend on this component.
- Please let us know whether this issue occurs in only your current Windows user profile or in a newly created local test account as well.
I look forward to your update.