The exported icon names are weird. It should be blabla-16, blabla-16@2x, blabla-16@3x, etc.
There shoud be a visual notification in the app when the generation of icons failed or succedeed.
I believe, there are better tools online, including scripts which you run yourselves and export your icons.
For instance, one I recommend is the "ios-icon-generator" on GitHub.
I had high hopes for this app, but it failed to deliver.