The ‘qtpro’ is a features found in the latest version of the store plugin. It may be that you are using the latest version of the SEO plugin on an old version of the store – the latest version of the SEO plugin (and all our additional plugins) are written for the latest version of the WPOLS plugin.
You could try to update to the latest version of the WP Online Store plugin (please back up your website before running any updates) or you may get away with ‘hiding’ the line of code within
which is trying to access the ‘new’ store feature. You can hide a line of code by putting // in front of it. This should be tried by those who are comfortable editing code. (Always back up before editing.)