Hello,
Try to do the following to update the theme:
1. Go to Dashboard -> WoodMart -> Theme License and deactivate the theme.
2. Go to Dashboard -> Updates and click on Check Again.
3. Activate the theme with your purchase code again.
4. Try to update the theme via Appearance -> Themes or via Dashboard -> Updates.
If it does not help, make the full backup of your site and update via FTP https://xtemos.com/docs/woodmart/update-theme-2/
If you need help, provide site admin as well as FTP access to the private area.
Best Regards