I have rebooted several times still receive same msg there is no other installation in progress
In fact not a LibreOffice question but a Windows problem - check here [Solved] “Error 1500. Another installation is in progress” Windows 10 (or any other sarch result on the net for error 1500 another installation is in progress)
I had the same problem trying to install 7.4.5.1 on a Windows 11 machine. I clicked on link in anon’s reply Oct 2020 and following the suggestions I found msiexec.exe was running (in Task Manager). After removing this task I was able to run the LO installation. As stated it is a Windows error and not specifically LO.