Upsell not showing anymore

Hello,

I use JCART upsell since 2 years already. But for some reason I cannot understand, today I tried to add an upsell then suddenly the widget disappeared on the Checkout page (it was there before I added the new upsell product).

Would you please solve this issue and explain me why ? I tried to remove the new added upsell, deactivate/activate the plugin, update the plugin (premium), but nothing work.

Thank you