Not opening pages in certain web pages

Over the past few weeks some web sites have not been working properly on my PC. The site will open but I am unable to open individual pages within the site. This has occurred only on a few web sites, such as the UK met office, while other sites, such as XC weather, are unaffected. I have tried the web sites in another profile, using private browsing and refreshing Firefox but there is no change. However, if I open the Mozilla VPN and then try the problem goes away. The web sites also work correctly when using the Edge browser and when using Firefox on my laptop and mobile.