Try this for the last time
Are you running an Anti-Malware/Anti-Virus App?
Yes I have McAfee and I accept Windows 11 security updates as and when.
Thanks Anke and Boban for your suggestions. I'm tied up next couple of days, but will try them when I get time.
Right - ensure that App Inventor is added to the 'trusted' or 'white list' of McAfee so that it does not intercept App Inventor and damage your project files. In my honest opinion, having used Windows since it began, Windows built-in security is all you need. Third party anti malware has a habit of producing false positives too.
I managed to install Companion v2.73ad2 and the problem of missing components has been fixed!!
In looking at some other error messages it seems that other people have been having the same problem.
I noticed on my devices that Companion v2.73a had had an update about 5th December - and it was after that the missing components issue started, but it seems only if the app has some extensions. I am left wondering how that update blunder (presumably by MIT??) could have occurred. It has certainly caused a lot of frustration.
But one question: When I run Companion v2.73ad2 a QR code pops up with a question about being out of data with two options 'Not Now' and 'OK'. I'm not sure what to select, because Companion seems to be working well for me as it is.
Select "Not now"