Apps not showing up in Files - / Locations ”On my iPad”

IPad Air / IOS 12 ...

I used to have my installed 3rd party apps showing under Locations / On my iPad in the Files - app .

Last night I did a full factory - reset and now they are not showing any more .

Though I’ve installed the same apps with the same Apple - ID .

For example I’ve made a mp3 export from Positive Grid’s Final Touch - app, but I can’t find the created mp3 - file anywhere .

Please HELP ASAP,

Toni .