I am new to Upwork and going to start my freelance business here, but my account is under review so I can't bid on any jobs. Please help me how should I do.
I don't think there is much you can do. Have you followed best practices* to ensure that your account is as complete as possible? I would also advise to check your email bulk/spam folder in case any correspondence from Upwork to you was missed.
Good luck. You'll get there.