Some websites not loading

[JRW92]

Since last Thursday I have found key websites I use for work are not loading properly.

My general internet use isn't affected and I'm still able to use social media on laptop and phone and streaming isn't affected so there is nothing wrong with the overall connection.

I work from home and nothing changed in my set up between Wednesday last week when things were working and Thursday morning when they weren't.

I have cleared cookies and cache in browser, tried a different browser, cleared DNS cache and rebooted  my router without any luck!

Help!!