[SOLVED] Suddenly asked for Authentication

[rogersim193]

I have used Mint 18.3 Cinnamon happily for some months now. Beside standard partitions, I have 3 spinning disc additional data partitions in fstab and they have always mounted at start-up as required, till today, after a break of a few days. The system works as before but the three additional partitions, although shown in the File Manager list on the left, when selected, trigger a message:

Authentication is required to mount ST.......(/dev/sdd5)
followed by a prompt for Password for root, which fails every time though the password works elsewhere just fine.

Selecting Details shows
Action: org.freedesktop.udisks2.filesystem-mount-system (which leads nowhere)
Vendor: The udisks Project (which leads to a repo which is beyond me)

I don't knowingly have or use any authentication and don't really want to interrupt my current project to involve it.

I have installed and used many LINUX systems and kept them going over many years (without having Windows or MAC), but am at a loss as to what this means. Google has thrown up little. Please help with a remedy or work-around.

[rogersim193]

Embarrassing! I found that it is not a mounting issue, but somehow I was no longer in the sudo group!
Rectified that in recovery mode and all is well.
Now off to another topic to explore how that happened