Nikon D750 - no code error

Doing this for a friend, I do not own a Nikon. But I have access to it.

Nikon D750

After lenses were switched, a 70-200/2.8 to a 24mm this started happening. On switching camera on, error is displayed, but no code of any kind. On pressing the shutter button, mirror flips up&down several times and nothing else happens. This is the case in any mode of shooting. Lens switching makes no difference. Camera worked fine before, so a sudden change.

Has anyone experienced similar issue?

Firmware screen is showing C: 1.10 / L: 2.015

And would anyone support the idea of updating firmware to latest version to see if it resets the camera? There is nothing in current update to 1.15 that appears related, but wouldn't it restart the system? Menu to this extent is available, so updating firmware appears possible (I have formatted SD card in camera now).

Is this of any help?
https://www.nikonimgsupport.com/eu/BV_article?articleNo=000005282&configured=1&lang=en_GB

This one is useful too:
https://www.stellarinfo.com/article/nikon-dslr-error-code-messages-and-fixes.php

Thanks for the links, but no, none of it made a difference. Looks like he needs to take it to service. I have updated firmware on it to latest version, but that also did not do anything. ERR appears to be either a small issue or who knows what one.

I would turn the camera OFF, remove the battery, turn the camera ON, press and hold the shutter release button for several minutes, then leave on with the battery removed for an hour or so then turn the camera off, install the battery, and turn the camera on. If it still shows ERR take it to service.

shutterfinger said:

I would turn the camera OFF, remove the battery, turn the camera ON, press and hold the shutter release button for several minutes, then leave on with the battery removed for an hour or so then turn the camera off, install the battery, and turn the camera on. If it still shows ERR take it to service.

Click to expand...

Pressing/holding shutter button for several minutes is not coming from Nikon support. What does that do? All else has been tried as it is one of ways Nikon provides.

Helps drain the power from the circuits, (charged capacitors).
If the lens were changed with the power ON then its likely a circuit was damaged.

shutterfinger said:

Helps drain the power from the circuits, (charged capacitors).
If the lens were changed with the power ON then its likely a circuit was damaged.

Click to expand...

Yeah, nothing helped. I don't know what he did, but he's had it since new and not a novice. I read quite a bit about this err, it looks fairly common.