This button used to work well, but it stopped working correctly. It's useless now.

Good idea

I also experienced the bug with nothing happening after clicking the button in toolbar (and no button appearing on images at all), turns out it was caused by FF content blocking (I also use container tabs for almost every tab and they cause no issue at all)
Edit:
The solution is to just turn the content blocking off for sites you wish to use Pinterest Save Button on, how to do that is here: https://support.mozilla.org/en-US/kb/content-blocking#w_turn-content-blocking-off-on-individual-sites, or turning the content blocking off completely, like described here: https://support.mozilla.org/en-US/kb/content-blocking#w_how-to-block-more-or-fewer-trackers

je n'ai jamais pratiquée

Clicking the button has zero effect.
Edit: It seems the bug has been fixed and it has been working perfectly (at least for me) for a while now. Very happy with the add-on now.

Simply does not work. Clicking the button does not pull up a pin/save modal on any site I visit, including sites where it used to work (Wayfair, Amazon). Leaving an unfavorable review seems to be the best way to get developer eyes on this, so hopefully you fine folks can make this extension functional again. Feel free to reach out to me for browser specs.

Like other users here I have been having issues with the Pinterest Save Button working off and on but with increasing frequency over the last few months. I've been in contact with their Support Team over the last week, but like others have mentioned, they don't seem too keen on actually fixing the issue.

The 1st person gave me a list of things to try, despite my having stated that I had already done so, & wanted me to send video as proof that I had done them. I sent screencaps & a more detailed description of the issue, including that there is a second account on the same computer, using Pinterest in the same manner, that is also having the same problems but didn't develop them at the same time/rate.

I was passed off to another member of the support team who seems to be convinced that I'm just not logged in, despite the screencap showing both my being logged in & the failed save screen in the same shot. They sent me a screenshot of them being logged into my account & successfully pulling up my boards as if they were going to pin a site, but when I went to do the same my boards ceased to exist in the pop-up (& yes, I was logged in. . .).

I don't know what the malfunction is, but apparently enough people are being effected that they need to make a mass announcement that it exists & that they are looking into it, then actually look into in instead of sending the same failed "solution" to the same people repeatedly.

Update 7/25
They decided, without telling me which browser or devices they were using that didn't recreate the problem, that they were done with me & closed my inquiry. So for anyone else that wants to contact them, make sure you find out what they're using to try to diagnose the issue.

Has not worked for a very long time. I would open, but it didn't recognize that I have a Pinterest account, so I couldn't save anything to my current boards. I uninstalled it and reinstalled it and now it does nothing. It used to be a great feature. Now it's worthless.

Love it very much. But it isn't working already for about a month :(

would never pull up anything when I clicked the button

When it works, it's great. But if Firefox updates...the troubles begin and you get a message saying "Ooops!" Very frustrating. After following pinterest directions for fixing the problem, I realized they just did not work. I've had to delete the button, close Firefox, restart, and then re-install.

In the past the button worked decently, now in a bad way!
Very frequently, the message 'Ops! Sorry, an error appears to have occurred. Please verify that you are logged in to Pinterest and try again. ' This support explains to you how to restore the functionality of the button:
- clear the Firefox cache
- uninstall the button
- reinstall the button
But are we crazy? Sounds like a joke!
At least try to find a solution to this bug would avoid the shame of being considered amateur programmers.
Otherwise, restore the old version that didn't give any problems!

Doesn't work

Despite the slew of other reviewers demonizing the Firefox Devs, it is abundantly clear that their issues are user errors not dev errors. :e: Turns out there is an error, but that doesn't rescind the fact that the prior reviewers are still dicks about it :)

I just installed the app, have used it perfectly fine.

I am logged into a single Pinterest account, and am running no other add-ons. As a note, I run very stringent privacy options and restrictions on both my device and Firefox, and I'm still not plagued with any issues.

Thank you Firefox Devs for being patient and doing your best, this is working great for me and my design work!

:e: I don't see a way to respond to the dev response below, so I'm editing it in.
I am running container tabs, but specifically I only had a Facebook container tab open at that time. To my knowledge I didn't have anything else actively running in a container tab, except for the Facebook one.

:e: I now got the login error myself, here's a capture of the error message & the error log text:
https://imgur.com/a/mJ3gBJR - Error capture
"Invalid URL
The requested URL "[no URL]", is invalid.

Reference #9.ae9a3b17.1562655664.4f2c2b8a " - Error log text
I was currently logged into Pinterest on a Tab, and I Reloaded the tab and still had the error. I was attempting to pin an image from Unsplash when I encountered the error.