Tooltip not working

Hello,
I have created a contact form with contact forms 7. It worked fine for some months, but when I recently checked my website I noticed that the tooltips are not displayed (neither the question mark nor the tooltip). I suspect that some update ruined something, but I’m not sure.
When I disable the plugin, the tooltip text is written next to the checkbox, so it definitely does something when it is enabled (the text disappears).

If you go on my website, the checkbox “Kostenvoranschlag berechnen” should have a tooltip next to it.

I am using the Divi theme and conditional fields.

I tried reinstalling it – no luck.
I tried resetting the style – no luck.
I tried selcting a different form, but that didn’t changed it!
I tried different settings in the settings Menue (e. g. Check this option if your website does not include Font Awesome yet.). – no luck.

Could you help me please?

The page I need help with: [log in to see the link]