Not authorized to perform operation - polkit authority not available and caller is not uid 0

I've a Dell Precision Ultra-Speed Drive Quad x16 card installed in Dell 5820 workstation in which 4 x ADATA 2TB NVMe SSD drives. Besides, 1 x Toshiba 2TB NVMe SSD drive (Ubuntu 18.04 boot) and 2 x SATA 16TB Segate IronWolf 3.5" HDD.

The OS is Ubuntu 18.04. I used GNOME Disks to format any of 4 x ADATA SSD drives, Segate 3.5" HDDs, it pops up the error of

Error formatting volume Not authorized to perform operation (polkit authority not available and caller is not uid 0) (udisks-error-quark,3).

I've no idea on this message. Suggestions are welcome.