I recently provided access to cloudflare and I was able to login into dashboard. But suddenly today I'm receiving 1001(unauthorized) error and can't able to login into dashboard.
In the past when this error was mentioned it was transient/was related to API issues which were fixed. I don't see anything on the status page about that nor any other complaints, are you still having the issue now? Would try diff browser/not auto fill/beating the captcha as well just in case. If you still can't access, you can submit an access issue ticket while logged out via: https://dash.cloudflare.com/login-help