The failure was caused by the following reasons:
1. The Attributes created in Products – Attributes do not appear in the selection box of XStore Linked Variations Options – Attributes
I created 8 Attributes, but only 3 appeared in the selection box of XStore Linked Variations Options – Attributes
2. After selecting Attributes in XStore Linked Variations Options – Attributes and clicking update, the Attributes disappear again. See the video for details:
https://www.dropbox.com/scl/fi/4bcozvn1rw4y0xfn9xf9g/2025-09-11-11.51.48.mov