Hello! Do you have a HelpDesk site installed? If so, please open it, then navigate to Settings > About and renew the client secret using the global admin credentials. The legacy authentication should be allowed in your tenant and the MFA should be disabled - otherwise, use an app password. Let me know whether it worked.
I bought a license yesterday. I tried to do an install and I am getting this error. I have logged a ticket with your support desk and still waiting for a response.
Hello Gumani! The instructions were sent you yesterday at 6:25 a.m. (UTC). Did you not receive them? In a private message, I specified the e-mail address which the reply was sent to.