If your login details are saved in browser, try pausing for a short time after you click your user name, before you click the password. I found that for me, signing in to quickly may trigger something to cause an issue. I didn’t have any issue signing in just now.
I was facing this issue just now. Thought it was because I was running a VPN - no. So, basically, I run two OSs: linux and windows. Sometimes I have this glitch where my clock gets readjsuted. I fixed the clock and the problem with the OpenAI login was gone. Hope it will help someone.