Unfortunately, even after reading the other topics about sidebars not showing up, I am facing the same problem. For as far as I could remember, I did not change anything through CSS, but forgive me if I did (I am working on several sites and am almost 100% sure I did not change the Travelify theme).
If I indeed not change anything, how could I solve the problem?
I hope you are well today and thank you for your question.
Please make sure you have not selected the option “No Sidebar, One Column” in the Specific Layout Per Post/Page and Default Layout Configuration settings as described on the following page.
If it doesn’t help you then please share me your site link so that i can troubleshoot it.