Everyone is appearing as a Steve or an Alex.

I've come across this bug before, but every time it occurs it normally naturally resolves itself after a certain period of time or after simply leaving and rejoining the game. But unlike before, the bug didn't naturally go away and/or fix itself and has been effective for months now. Skins that have been saved on the computer beforehand do appear though. My brothers have their accounts on this computer along with their skins saved in the Minecraft skins folder and so playing with them (when they play from a different computer) their skins appear because I have them saved but the skins of other players whose skins aren't saved on this computer don't appear. I've tried looking up how to fix this but either the method is outdated or doesn't work. I'm on Windows 10 and I've just recently updated it to it's latest version. This issue hasn't always been happening on this computer; skins on Minecraft server used to work just fine. Thanks.