Why would the Ubuntu installer sometimes detect windows and sometimes not?

[kalpana]

Hi, I'm trying to set up my machine as a dual boot machine and have done so on many occasions. I'm running Windows 10 and I'm trying to install Ubuntu 20.04. It appears that sometimes the installer detects Windows and sometimes it doesn't. Usually when I try a second time it finds it however, on this occasion I've now tried multiple times and it still hasn't found it. I don't suppose anybody might know what the problem is?

Regards

Nick