Steam?

[Emil]

Sometimes if you have an anti-virus software like Mcafee it blocks steam.

Go into your antivirus software>Settings>Disable Firewall.

That what worked when I had this problem.

DO NOT TURN OFF THE FIREWALL.

There's a reason it is there, to protect you against viruses and shit, turning it off makes you vulnerable even if you're very careful with what you do on the internet.
Apologies for sounding like an overprotective adult or whatever. I'll edit this post with a guide on how to enable steam if it's blocked

Tutorial for anyone who is even slightly new to anything computer related:
Step 1: Search for Firewall. Depending on your operating system, the search button can be a few different places. On Windows 10, it's easy to find as it is right beside the Start menu. I don't remember where it is on Windows 8 or 7 (I think it's located in the Start menu on both of those, although Start looks very different on each of those so I can't explain it properly.

Step 2: Find the one named something like "Allow a program access through the Firewall". Since my PC is in Danish I don't really know what you have to find on any other language.

Step 3: Find Steam (or whatever program you want to allow through).

Step 4: Tick on Private and/or Public access.

Step 5: ???

Step 6: Profit!

In case you can't find it, just tell me and I might be able to help you.