There are tons of complaints in the forums that the Google PageRank went missing in action and is no longer working.
The issue is not with Toolbar PageRank, but rather how 3rd party tools lookup the PR values. Google did make a change, they changed the lookup URL for the PageRank value.
There are dozens of complaints at DigitalPoint Forums, WebmasterWorld and Google Webmaster Help.
The issue, as explained well by David Naylor is that they changed the lookup URL.
Old URL:
http://toolbarqueries.google.com/search?client=navclient-auto&features=Rank&ch=8f3b58e04&q=info:[URLHERE]
New URL:
http://toolbarqueries.google.com/tbr?client=navclient-auto&features=Rank&ch=8f3b58e04&q=info:[URLHERE]
So if you really want to check your toolbar PageRank, use Internet Explorer and it should work.
For the rest of us, back to work.
Forum discussion at DigitalPoint Forums, WebmasterWorld and Google Webmaster Help.

Comments:
SearchRocket
10/06/2011 12:49 pm
There's a little more to it than [URLHERE] because the ch parameter must be calculated for each URL. If you have existing code that works though, just changing the path from /search to /tbr is all you need to do to fix it. The change occurred at 3:45am BST today.
Önder 'Vincent' Koç
10/06/2011 12:56 pm
http://www.bighitmedia.co.uk/google-page-rank-fix/ We also reported this the same time arround David Naylor, seems though PR is there but google.com is hitting n/a
joshua
10/06/2011 04:10 pm
I can't get it to work... no page rank for me :-(
Gareth
10/06/2011 05:15 pm
This explains a lot. I wondered why I was having issues while writing my page rank article today
SEO Expert In Uk
10/06/2011 08:07 pm
I have some serious issues because I just put together my two tools which show up the page rank. Now they show nothing so I am stuck on how to fix it in the code from the back end perhaps someone will be able to enlighten me or something as I have two useless scripts right now...
Amassine Omar
10/07/2011 12:10 am
thank you for this update
Thiago
10/07/2011 12:15 am
Works for me, thank you!!!
En Noticias
10/07/2011 12:17 am
Thank for this...www.ennoticias.net
Graham Ginsberg
10/07/2011 01:23 am
http://www.bighitmedia.co.uk/google-page-rank-fix/ [NAME]=Google pagerank[TITLE]=PR[URL_R]=http://toolbarqueries.google.com/tbr?client=navclient-auto&ch={gchecksum}&features=Rank&q=info:{url|encode}[REGEXP]=Rank_.*?:.*?:(\d+)
James Junior
10/07/2011 02:24 am
I used the new URL in the example below to fix the Firefox Webrank Toolbar at http://www.naples-fl-real-estate.com/2011/webrank-google-pagerank-fix/
Green Tea Wonders
10/07/2011 06:05 am
This is a big relief! It worked fine for me. Thank you.
JeanPaule
10/07/2011 06:15 am
No, Pagerank is not dead, it's just changed URL (in french : Non le Pagerank n'est pas mort, c'est juste qu'il a changé un peu de syntaxe) http://www.rss-info.fr/Pagerank-nouveau-algorithme-pour-afficher-note-du-PR-changement-code-source-001100 You also can see your pagerank site on : http://www.pagerank-update.com
Damu
10/07/2011 10:22 am
new url works for me. thanks for sharing.
NiX
10/07/2011 05:23 pm
Thanks for this post. I've updated the new URL. If you need free non-OCR PR checker server with PR icon generation: http://myproxylists.com/google-pagerank-checker
Hasan Agh96
10/07/2011 09:03 pm
it worked here thx a bunch
speed up pc
10/08/2011 03:47 am
I tried the new url and it worked!
Essex Boy
10/08/2011 08:22 am
So does this mean all plugin / addons need updating too before it works? I use a Chrome plugin, noticed that was not working anymore.
RobK
10/10/2011 01:33 am
Let's just hope that the 'tbr' in the new URL "http://toolbarqueries.google.com/tbr?client=" doesn't stand for "to be removed"... with toolbar PR to be gone soon?
Maxxi
10/11/2011 01:21 pm
Another challenge and back to the drawing board.
Essex Boy
10/11/2011 02:43 pm
Well, PageRank Status (Chrome plugin) is working again. I did not update it, so I guess something changed again?
Liza
10/11/2011 04:48 pm
It lok likes "tbr?client=navclient-auto&features..." do not work anymore.
Anand Meena
10/12/2011 10:10 am
Thanks for updating me, it is working for me.
Cindy Cloughly
10/14/2011 01:12 am
I'm on Firefox, and Pagerank isn't working on my GOOGLE toolbar. What gives???
Essex Boy
10/14/2011 01:28 am
SEOBook's Toolbar PR works. Give that a whirl?
jameswade
10/17/2011 11:56 pm
You'll also need to update your code on your websites. Updated code can be found here: https://github.com/phurix/pagerank/
kevin
10/29/2011 05:30 pm
Google probably done it becuase they were getting to many automated 3rd partys looking up page rank they dont seem to like third party people with page rank atall
Douglas W. Palme
03/05/2012 10:16 am
Why would I want to use an inferior, virus susceptible browser just to do a page rank lookup, especially when page rank no longer holds the value it once did. With Pandora, PR is not considered that important of a factor and even Google says to ignore it.