Mobile Theme Not Working on Tablet

Hi, I was hoping someone here might be able to help with my tablet problem.

I’ve recently migrated from wordpress.com to a self-hosted platform and I have imported my site and uploaded it as it was on wordpress.com. There is an issue however with the responsive layout when displayed on tablets.

Previously the sidebar would position itself below the content for ease of reading, but now it keeps hold of the desktop layout. The site in question is https://www.riventine.com, which you can compare to the free version https://www.riventine.wordpress.com. Everything is the same excepting a couple of widgets like jetpack but I have disabled them in testing and the theme still does not respond to tablets.

I am using the suits theme in case that is important. I have tried reloading a backup as well as switching themes and then switching back but the problem persists. I have a feeling it may be something to do with CSS despite my not altering anything, but I really wouldn’t know what I’d be looking for ??

Any help would be greatly appreciated ??

EDIT: I forgot to mention I have enabled the mobile theme option in Jetpack and it works fine on mobile phones.