Lacie not mounting w/ Thunderbolt

[Oktober]

For some reason my Lacie 3TB external HDD will now not mount to my iMac when I connect via Thunderbolt cable - The hard drive light flashes and that is all. However, when I connect via USB cable all is fine.

The Lacie is formatted to Mac OS Extended (Journaled).

Any help and advice on how I can fix this issue, that would be great.

 

[Bigwaff]

The iMac is the one in your signature? What model year? What model and year Lacie external HDD? Connected via Thunderbolt 1/2/3 ? Any adapters or docks in the mix?

 

[MarkC426]

Try another TB cable maybe.
The drive sounds fine if it works with USB.

 

[Oktober]

Apologies all. yes the Mac in question is the one listed in my signature, late-2015 27” iMac 5k running Monterey (which I have just done a fresh install of OSX Monterey - latest update).

The Lacie hard drive is a LaCieD2 3TB thunderbolt 2 (see attached pictures).

As the drive works fine connected via usb, there must be a problem with the thunderbolt side of things. But the light flashes on the LaCie when connected via thunderbolt.

 

[MarkC426]

I know this is a different model, but may be relevant

d2 Thunderbolt 3 has a Red Flashing or Solid Light | Seagate UK

 

[Oktober]

I know this is a different model, but may be relevant

d2 Thunderbolt 3 has a Red Flashing or Solid Light | Seagate UK

The front of my LaCie just flashes blue when connected via thunderbolt (and USB - when active)