Maybe Windows 11 is to blame? Is also only a BETA version and only in 2 years is all the BUGs removed!

11 is not beta. MS released it about three weeks ago. And it is shipping on new computers now.

I have updated the WebsiteX5Pro to v4.7.  It opened one project 4.5 wouldn't open, but I have one other project hat I am still unable to work on.  Why is this?

I should have included this picture of the open error message in the previous post.

I have tested it and a V2021.4.5 project goes to convert normally to V2021.4.7 with no errors.
So it can only be a bug in your project that it throws this error. Also, I see that you have saved your project to an Onedrive cloud storage. Maybe it's because of the cloud?

Hi Andreas.  You changed my question.

My question was,"Trying to open a 2021 v3 file using 2021 v4.5.  It won’t open.  Why???

Since then, V4.7 came out. So now my problem is that I am trying to open a 2021 v3 file using 2021 v4.7.  It won’t open.  Why???

However, I am glad to hear 4.5 converts to 4.7 ok.

I found a workaround. Don't know if this works on all occasions, but this worked for me on this particular file. I duplicated the version 3 file. At first duplicatio did not work. The program created a directory for the duplicate (1) project, but it was an empty directory. The program said it did not have permission to write to the directory it created. Strange.

I deleted this new directory. I then tried to duplicate the v3 project again. This time it duplicaed the project successfully. I then was able to convert the duplicated project from v3 to v4.7.

Then just for giggles, I tried to convert the original version 3 project again. It still does not work. So I deleted the project and renamed the v4.7 project to remove the (1) from the name. Voila!

Hello Gregory

Unfortunately, it seems like the error given during import indicates that some part of the main project file is corrupted.

If you solved this by duplicating it in the previous version, it is probably because during the duplication, the corrupted part gets removed and you get a working copy of the project

I confirm that this is probably an issue with the project itself and not the new version

Should you encounter any similar problem at a later time, please let me know here

Thank you

Stefano