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.

Essa bagaça não funciona, não aparece nenhuma opção, tela ou mensagem e clicar em cima do botão na barra de tarefas não faz nada. Em vez de refutar as reclamações consertem essa joça ou retirem ela.

This button used to work prior to updates from Firefox. No matter what I do to fix it, it will not work. I keep getting an error message stating "Oops, something went wrong". Using Firefox 67.0.4 (64 bit) on Mac Mojave.

This add-on was great until recently, when it stopped working. I keep getting the same error message others have mentioned: "Sorry, something's not quite right here. Please check that you are logged into Pinterest and try again." I am logged in! Ok, so I logged off, cleared cache, removed and reinstalled the add-on, tried again many times, but no joy. I use Firefox version 67.0.4, MacOS High Sierra 10.13.6. I no longer use Ghostery. Wonder if there's a fix in the horizon...
Answers:
Are you using more than one Pinterest account? No
Are you browsing in private mode? No
Are you using container tabs? No

Not sure what we'd talk about away from here. I'll tell what I do and have been doing for months till this button stopped working: I'd go to my Instagram page, click on a photo/post, click on the Pinterest Save button, a window would open up to give me options to save to my Pinterest account, and that was it—until I started getting the infamous "Sorry, something's not quite right here. Please check that you are logged into Pinterest and try again." I didn't do anything different, it just stopped working.

This doesn't happen with the new Pinterest button I'm using now. I'm guessing it's related to the way Firefox handles add-ons now, and for some reason yours isn't cutting it. Maybe check with them and the changes to their new version?