Problems after installing GanttProject 3.3 Beta

I have been using GanttProject 3.1.3103. I had created two .Gan files. One was my baseline project and the second was the actual project status, with updates to percentage completion and changes in some tasks dates. Both files were displaying the GanttProject icon on the left hand side in my saved folder.

After reading various threads, I decided to try out 3.3 Beta. After I downloaded it, I now had two versions of GanttProject on my laptop.
However when I went to my saved folder to click on my previously saved .Gan files , neither one of them was displaying the GanttProject icon on the left of Filename and neither file would open. An error message came up. Sorry I forgot to screen capture this message, but it said something about

However when I opened the app itself (both version 3.1 and 3.3 Beta), and I then selected Project > Open > … I can see both files in the GanttProject pop up menu. I am able to now select either file and it opens properly.

I then went back to my saved files folder, selected each file in turn, and used the Open With option to located my 3.1 version, selected it and now the files open like previously.

Anybody here with a similar experience ?

So do I, but not installing them. I use the .zip and JRE Full .zip files.
There are common config files, as the “.ganttproject” file read and written by all GP versions.

File associations (what program can open files with this or that extension) and file icons on Windows are controlled by registry records which are updated by the installer. Installer for GP 3.3 Beta was built using a new tool, so perhaps there is something wrong with the registry records.

We will build the same installer for the release build. Meanwhile, you can set up file associations manually.

Thank you for this clarification.