safari can't reload off-line saved reading list items
Had the same problem. I think it's all about permissions and privacy.
I did this and it's helped:


Pull down the  Apple menu and choose ‘System Preferences’
Choose “Security &amp; Privacy” control panel
Now select the “Privacy” tab, then from the left-side menu select “Full Disk Access”
Click the lock icon in the lower left corner of the preference panel and authenticate with an admin level login
Now click the [+] plus button to add an application with full disk access
Navigate to the /Applications and choose “Safari” to grant it Full Disk Access privileges
Relaunch Safari and try to open saved pages in offline mode