Book disappears from 1 computer but not another

Spanish to English
Mac OS Sequoia
Studying Isla de Tesoro RL Stevenson on one computer Mac OS 12. When switch to the newer computer that book and apparently only that book is not in the database. Saved words from the Isla de Tesoro appear in the Saved Words database, but linking back produces “File not found” error

Language Reactor Isla de Tesoro absent
From Mexico