Same here. No matter what I try, I keep getting the same error for two days straight. I tried contacting the Steam support team after exceeding the number of tries and even that doesn't work: I get a "We have trouble reading your captcha" error, even though it is 100% correct.

Me too. I can't get my old email back, and I can only get into steam from the steam client on my pc. Luckily I left it logged in. I just got a new pc and I can't play anything until this gets resolved. I tried everything I could find on reddit and other sites but nothing works.

I couldn't use my email since I don't have it, I tried the next option of logging into paypal to verify but that didn't work either (even though immediatly after I bought a game with the same credentials and it worked fine). The final option is to send a help message and but after I fill out all the info, get a code from my new email and hit continue it gives me the captcha error. I've looked at pics and videos and there is supposed to be a captcha there but it's missing on mine, which causes the error. I ended up sending a message about the game I bought explaining all of this, since I techincally can't play the game until I get my steam account on my new computer.

Someone resolved my issue the next day. You need to find another way to contact them and explain your situation. I did through a recent game purchase.