We have received several reports about Master Admins gets an error message "Your administrator has not granted you access to QuickBooks Online Plus. Please contact your system administrator with any questions". Our Product Engineers are now working to fix it as quickly as possible. While they do, I recommend reaching out to our Customer Care Team, so you'll be added to the list affected users (INV-51953).
To reach them, click the ? Help button at the top-right corner and select Contact Us to talk with a live agent. Ensure to review their support hours so, you'll know when agents are available.
We appreciate your patience while we work for a fix. If you have additional assistance while managing your QuickBooks account, let me know. I'll be around to provide further assistance. Have a nice day.