Just switch on or restart the MS server?

I help out a small office with my limited IT knowledge (I use to work for them as a 1st line support years ago and forgotten the simplest things now that I do something else).

They basically lost the network and internet access days ago but with the help of an IT company that does support them via email they've managed to get the internet back up but no access to the server folders and their Wi-Fi (an AP wired to the Aruba switch) does not work.

They've got a Fortinet firewall which the switch connects, both share rackmounts with various companies on the serviced office floor. Then somewhere in the shared server room there is a PC that sits on the floor which has the server on.

Apparently, this PC switched itself off somehow. The IT support company has quoted £1000 for them to physically come to the office and check everything.

Therefore and before they bite the pillow, they've asked me to go in and take a look myself and see if I can get it up and running.

Assuming it is off and I switch it back on, and say there's nothing wrong with it, should there be no need to log into the server?

I know the name of the server and IP address, whether or not the username and password has changed is another matter.

To start, will it be a case of logging into a client machine as an administrator, but then what?

Do I open up a browser and type the IP address or name of the server starting with \\\\?

Do I open Windows Explorer and use one of the above?

I'm embarrassed to say I really can't remember!

I'm sure it'll be like a trip down memory lane if I get in.

Thanks very much and hope you can help.