since recent upgrade, multiple ( but not all) sites result in 'proxy server refusing connection'
Additional System Details
- Shockwave Flash 27.0 r0
- User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:62.0) Gecko/20100101 Firefox/62.0
see this answer:
Do you need to use a proxy?
You can check the connection settings.
- Options/Preferences -> General -> Network: Connection -> Settings
If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.
See "Firefox connection settings":