Lol right? First of all, the OSBot client is NOT down, only Mirror Mode is down until they update with the new OSRS update, Stealth Injection works fine although let me say it in case you havent been told, do not use Stealth unless you are 100% willing to lose the account and quickly.
Second, I had the EXACT same issue after the last update. Tried everything, restart, pc restart, deleted OSBot folder which I quickly regretted, you name it. What finally fixed it for me was simply clicking on the red "Sign Up" hyperlink on the initial OSBot launch window, then close the webpage if you want, then close the OSBot Client and restart it.
I've seen far more odd fixes for things before, but I was fuming/laughing/crying after I spent almost 2 hours trying everything in the book and waiting for a response on the Forums. Hope it helps!