You can try reverting any changes made to the code of .liquid files by these apps in the Online store > Themes > Actions > Edit code menu.
Thanks for reaching out.
I appreciate that you have included a link to your store as that is super helpful! It looks like there is indeed an error when you attempt to add a product to the cart from within the online store.
Did you happen to make any coding changes to your theme? As suggested above, we can roll back to an older version of your theme. If you would like to revert the theme, you can navigate to Online Store > Actions > Edit Code. Once you are looking at the coding of the theme, you should be able to see an option to use Older versions of the theme. I took a screenshot from my test store to show you the section I am referring to:
Let us know if that fixes the cart error you are experiencing.