Create a table of contents using PlutoUI and there you can find the label for the hyperlink:
In this case the label is #156ae8d5-9cf3-4e57-86d1-76afb9d92cb9.
In this notebook, this link works:
[Sol 1a](#156ae8d5-9cf3-4e57-86d1-76afb9d92cb9)