Related to this request:
Batch relink to CC libraries
https://illustrator.uservoice.com/forums/333657/suggestions/31902295

Someone mentioned once you have your file how you want it to save it then move the images to another folder to "confuse" Illustrator then it will let you update all links. That is just not possible when you are sharing a server across a company. They really just need to make it like InDesign where:
A) it just remembers
or
2) you have import options
or
iii) you can relink via a folder you know everything is in, whether it is many instances of one link or many different links

Not seeing my post yesterday, so here's the shortened work-around:
1. Ensure new image size identical (at least proportionally) ro one to be replaced
2. Rename old (geekily, I put '404' on the end)
3. Open Illustrator layout file
4. Due to the linked file name change, Illustrator can't find it, so check the 'Apply to all' box and select your new file
5. Save the layout (Save as if duplicates are needed)
6. Remove the '404' (or undo whatever you chose to do) from the old file name.

Not ideal, but works for my step/repeat files

I work old-skool, in other words not using Libraries, but saved images in an image folder on the disc/server, preferably in a 'job' folder... So until they sort out this shortcoming, here is a solution...

To batch relink, either rename the folder or the image, I favour putting 404 on the end of the name (incase I forget to remove later, I'll remember what 404 is for)...

Now when I open the Illustrator file, it can't find the link, so I can direct it to a new folder or image checking 'Apply to all'... Save the file and remove the 404 from the files or folders you added it to.

Not ideal, but works...

Re-linking multiple images at a time would be a great time saver when you inevitably unlink all your files because a folder moved or you switch to a new computer. This is also broken when re-linked to a CC Library.

Meanwhile, check the external solution:
https://github.com/dumbm1/ai_scripts/blob/master/ord/fastRelink/fast_relink.jsx

When the same .psd is placed multiple time, Ai can't replace all in one go. It had to be done one by one...

I can just say that issues with Illustrator Links window are MANY and should be among top priorities for Adobe developers. Just use what you already have in InDesign and copy the way it works to Illustrator, like grouping same links, ability to relink all links by selecting group, adding go to link option on right click... just try to use right click on any link in illustrator, and you will see how much we are missing out, spoiler alert, it does nothing... or adding Alt + click option to relink so you can relink all, anything will be better than having no options what so ever. By the way I've been working in printing industry for 15 years and currently I'm working as a graphic designer at McCann Serbia, and this issues is really really really affecting our workflow, as it is forcing us to not use Illustrator in scenarios where it should be easier to use than InDesign. Hopefully we will get some update on these issues somewhat soon. It's really a big issue for Illustrator users in my opinion. Thank you for your time.

Definitely needs to be an option to relink all instances of an placed image. In some of my documents, I have many (sometimes 100's) instances of a placed file. I have to select the file and place each individual instance and it is very time consuming and cumbersome. If I decide not to go ahead with relinking all of the instances, I get stuck in a loop of still having to cancel each relink of each placed image. There is no way to get out of it. I do mock ups of cheer bows that have placed images of rhinestones to make it look realistic. If I want to change the colour of the rhinestones, I have to relink each individual rhinestone.

Just change other artwork to the same name as your linked file for temporary.. then change it back once you have saved your files. that's what i did, I'm on printing business too.

my files have multiple placeholder images which i'd like to change in bulk.
I want to be able to select multiple images and relink with the same file - with 1 click (bulk)
Attached demo action - "Relink All" > selected file will replace all selected images on file.

<https://github.com/dumbm1/ai_scripts/blob/master/jsx/fast_relink.jsx>

I tryed this Script, but I have a problem, I need to relink a lot of files to page 2 from a pdf.
Is there a solution for it?

the fast_relink.jsx do not see the PNG files to relink. It does see AI files.
Help with this, please?

it is TRULY unacceptable that this isn't already included in AI. Ridiculous. I'm going to spend an hour relinking each file one-by-one because I needed to move my image files around?

Any Idea of this?

Add a 'relink all instances' option/checkbox in relink file dialog box.

There should be a checkbox to relink ALL INSTANCES of a specific link with a new image in one go.

How to use this script?
When I go to File>Script>fast_relink.jsx

it pops up an error message in russian saying

"44 Файл для релинка не выбран"

or

24 Выделите линки и/или растровые изображения

It would be very helpful to have identical linked images grouped like in InDesign and hence to be able to replace all instances in one go.

I have a document that has many images, with the same file name. I think there is a problem with my OneDrive, where the files are linked on my work Mac, when I open the same file on my Mac at home they are missing. So I am constantly having to relink them when I change Macs. The problem is, when I select all the images with the same name it is not updating them all. I have to individually double-click each file to update them. This never used to be the case. Very annoying.

I'ts a known ********. But happily we have a script to relink multiple images with one file:
https://github.com/dumbm1/ai_scripts/blob/master/jsx/fast_relink.jsx
Huge thanks to Marat. Shame on the guy who works with relinking in Adobe.