MacBook Pro says it can't connect to server even though it's connected to Wifi.

> I did notice that I was unable to switch off the proxies (HTTP & HTTPS) as advised, the toggle kept switching back to 'on' automatically

This is a red flag to me.

First off, you should have control over this option being on or not. If you're unable to turn it off that indicates something is amiss.

Now, there are valid reasons for running a proxy, especially in a managed corporate environment, so the proxy itself is not necessarily a problem, but the question is whether you expect to be using a proxy or not, and what the proxy server settings are set to.

If you're unable to turn it off, that could be a managed environment that's forcing it (is this your personal machine? a company-owned system?), or it could be malware that's trying to force your system to funnel all its traffic through their malware system.

The tricky thing, of course, is how to fix it if you can't get online. My first thought would be to use Chrome, since it has its own proxy settings outside of the OS, but if you can't get online to install Chrome then that's a non-starter.

Second option would be to see if the same situation occurs in Safe Mode. Boot your system in Safe Modee - Apple Support and see if the proxy situation remains.

ashj77 wrote:

I haven't been able to go on any apps or browsers online on my MacBook Pro for the last 2 days. [...]

I wondered if this suggested a virus issue but I haven't been able run a separate virus scan (currently just have standard firewall), as I can't access the internet to download a virus checker so am pretty stuck. Any suggestions?

At the risk of insulting your intelligence - not my intention - but have you tried turning off the Firewall entirely?

Block connections to your Mac with a firewall – Apple Support (AU)

Have you tried restarting the Mac in safe mode and making your network adjustments?

How to use safe mode on your Mac - Apple Support 

Safe mode will often correct weird software behavior by forcing the OS to clear caches, do disk repair and other self-maintenance and housekeeping and temporarily disables third-party mods.

Does the same problem exist while in Safe mode?

You can exit safe mode by restarting your Mac normally, then reevaluate the problem.

if you are behind a Router you control, and enable a Wi-Fi password, your over-the-air messages to your Router are encrypted.

Re: Mac Firewall:

Your Router 'acts as your agent' on the Internet at large, and your local IP address is never sent off your own local network. Your Router ALSO has a built in state-wise firewall, and typical setting will cause it to discard any unsolicited incoming requests. Only answers to your DIRECT queries are allowed in. Your Mac is Un-reachable for unsolicited communication from the Internet at large. 

As long as you are using your own Router, there is no need to activate the Mac firewall. On public Wi-Fi, at the Airport or coffee shop, then maybe the Mac firewall would be a good idea.