Hello,
Thank you very much for choosing our theme and for contacting us.
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 we shall do it for your via FTP.
Best Regards