Constant "Matchmaking failed" notifications on my computer.

I have been experiencing this problem recently. Whenever I try to start games on my computer, I receive these notifications stating "Matchmaking failed. Please wait a few seconds and try again." I tried methods, like clearing my browser cache and cookies, restarting my computer, switching to incognito/private mode, switching browsers, and I receive the same exact notification every time I try to start a game. I played on mobile and turned data usage off, and I was able to play on mobile, indicating that there was no problem with my internet. Also, my computer has been really slow lately, and I'm suspicious of a possible virus causing serious issues. Can anyone help me find out why this is happening based off the information above? Thanks for your attention.

Note: This problem does not happen when I'm playing on mobile. 

It happens when it says that I'm connected, but it often says I'm often disconnected.