In regard to limited simultaneous connections:
You know guys and gals, it may be your ISP - I know it is mine. I have a CyberPower Fang III with i7, 64GB RAM, Dual SLR Nvidia Titan Black GPUs and a 1250w PSU on Win10... So no performance issues at all - but once my computer hits the 18th character I get a cannot connect to server error for 19th. I noticed that I cannot grab my laptop and log in either.
It is probably an anti-bit torrent/piracy DRM protection system in your country throttling your computer and restricting multiple outbound connections since it may seem you are uploading multiple files to outside recipients.
The only thing I can come up with and I have seen this complaint surfacing everywhere recently. Some have even complained (like at Bleeping Computer) that they have recently been restricted to a number of open Chrome instances on their computers also - like you have 20 open internet browsers and the 21st won't connect.
I suppose the logic is: "Why would one person need so many simultaneous internet connections?"
I don't know for certain but it is an educated assumption.