Nope, no issues here. For most of those browser switches, a reload might have been enough.
High scores are kept on a different server than the game. Whenever you go to face the top50, the game first fetches the top50 list from the high score server, then picks an opponent from that list.
If something prevents you from getting a connection the high score server, you end up not finding an opponent.
If this is a temporary issue, reloading the page or loading up the trainer and checking the high scores there might work (reset the connection, sort of, similar to what you would do if you can't save).
Next step would be to wait a bit and then try again. The server might be overloaded, or there might be some unit on the way between you and the server that isn't feeling well.
If this isn't temporary, it's quite likely that something is blocking the connection.
If it's some type of content blocking that you have control over, disabling it should give you confirmation that that really is the issue, and you can then try and fix the set up.
If it's out of your hand, you're probably at work or in school and might be better off doing what you're supposed to do instead, so you don't end up unemployed or expelled.