The game tried to "update" the layout file (e.g., rewriting cache data into it). Your anti-virus software quarantined the write operation, or the folder is set to "Read Only." Consequently, the file remains in its old state, triggering the "missing updated" flag.
The error message typically occurs in Assetto Corsa track shutorevivalprojectbetamainlayout is missing updated
using 7-Zip or WinRAR; do not just drag and drop the zip into CM if you are getting errors. The game tried to "update" the layout file (e