Error when open app.pro with Qt Designer

[HartmannSa]

Hi,

I tried to install the Qt based CAO Model Editor. However, when I want to open the app.pro file the following error occurs:

An error has occurred while reading the UI file at line 1, column 1: Start tag expected. Do you want to update the file location or generate a new form?

I can select "Update" "New Form" or "Cancel". I tried all, but I dont get something useful.

I am using QT Designer Version 5.9.5 and on Ubuntu 18.04 LTS and followed all your install instructions.

Thanks!