3CX Webmeeting can only share whatever Chrome has access to.
If certain apps do not appear in the share screen, it means your browser cannot see those apps for some reason on that specific computer you are using. Perhaps you should try this on other computers too and try to find what prevents Chrome from seeing your apps. Perhaps Chrome is not running with sufficient rights to be able to capture those apps.
By the way, in your screenshot above, it appears that neither Word nor Powerpoint were running at the time. Chrome can only share windows of apps that are currently running.