I have the same issue, Excel is broken.
Inside the excel I get the debug info:
Warning: “continue” targeting switch is equivalent to “break”. Did you mean to use “continue 2”? in XXX\wp-content\plugins\advanced-cf7-db\admin\class\PHPExcel\Shared\OLE.php on line 290
Call Stack
# Time Memory Function Location
1 0.0001 431504 {main}( ) …\admin.php:0
2 14.790 37623784 do_action( ) …\admin.php:175
3 14.791 37624160 WP_Hook->do_action( ) …\plugin.php:478
4 14.791 37624160 WP_Hook->apply_filters( ) …\class-wp-hook.php:311
5 14.844 37860368 Advanced_Cf7_Db_Admin->vsz_cf7_save_setting_callback( ) …\class-wp-hook.php:287
6 14.844 37860416 vsz_cf7_export_to_excel( ) …\class-advanced-cf7-db-admin.php:858
7 16.336 39216352 PHPExcel_Writer_Excel5->save( ) …\class-advanced-cf7-db-admin.php:1293
8 16.543 39418368 spl_autoload_call ( ) …\Excel5.php:181
9 16.543 39418416 PHPExcel_Autoloader::Load( ) …\Excel5.php:181