Black screen after champion select patch 5.14(maybe) and 5.15(definetly).

So I can't remember if this happened during the 5.14 patch but its happening a lot more frequently now that 5.15 is out. I've read multiple solutions to this problem and attempted to resolve the issue but none have worked. After locking in all the champions, the game counts down from 10 or whatever and then starts the loading screen. Where the loading screen should be, a black screen resides. After about 10-12 seconds i get a message box that says "Could not connect to server, please enable a connection to the internet and try again." or something like that. I know i'm connected to the internet yet it still gives me this message. People have been saying that its firewall, graphic cards, and a whole bunch of different things cause the problem. Anyone know a good solution? i've reinstalled, repaired, contacted support, and deleted files to force a re-patch and none of those have worked so far that i can tell. What's weird is that when i log onto my second account, there doesn't seem to be a problem. Like everything loads fine. I reinstalled twice and something must've fixed it because i could play for like a day and now it happened again but nothing is working pls help little poor old me