The solution depends on the cause of the issue, but of course, this is not always very obvious. With every YITH license, you get premium support, so if a plugin is not working as expected, this is a good start to ask for support. To help find the cause, you can always try a couple of things yourself like testing on staging, turning off other plugins or, moving to a default theme. Sharing your findings will greatly help us find a solution, or direct you to the third-party developer to get in touch.
If you have Elementor Pro, you also receive support, so this is another avenue to pursue to get your site in order. Who to contact first all depends on the cause of the error. The good thing is that we are in close contact with the Elementor team, though often it is faster to get in touch with them directly.