Ah, thanks for the lead!

Yes, we applied the code per the instructions you provided. However, it so happens that our theme (Avada) was updated yesterday from 7.4.1 to 7.4.2, so the changes we applied were overridden.

Solution:

After a bit of research, we learned that custom changes have to be applied to the CHILD theme, not the MAIN theme. So, we followed the instructions for setting up a child theme with Avada.

Once we installed Avada's child theme, the instructions you provided worked (and will now "stick.").

We're back in business.

Again, thank you!

it seems you've added this code directly in the plugin codes, haven't you? 

Please note: all changes made directly in the plugin codes are always lost after the plugin update. You should add the changes based on the interaction, provided here:  https://wpdiscuz.com/docs/wpdiscuz-7/customization/custom-template-and-style/

The tooltip CSS codes provided below (click on link) no longer work after updating your plugin to V7.3.0.

Tooltips for Vote Up and Vote Down Icons

Please provide updated CSS codes that will work with V7.3.0

Thank you!