If you are unable to auto-update SEOPress PRO, you can do it manually.
From your WordPress admin
For that, go in your WordPress administration, then Plugins.
Disable and then delete the SEOPress PRO extension.
No database data will be deleted.
Then, click Add, send the ZIP file of the downloadable extension from your customer area.
Activate and that’s it!
Using SFTP client
Download and install a FTP/SFTP client like Filezilla, Transmit, Cyberduck etc.
Ask your webhost your FTP/SFTP credentials to sign in to your server.
Once done, connect to your server and go to wp-content/plugins directory.
Delete wp-seopress and/or wp-seopress-pro folders.
Once done, send the newest versions previously downloaded from your computer to your server.
Then go back to your WordPress admin and enable the plugins.
If the last step was already done, disable SEOPress Free and PRO and reactivate them to make sure all activation / deactivation hooks are correctly executed.