Safari 9 - I cannot install extensions

I have tried most of the advices down there. None of them worked 😟

Then i have noticed the url & changed it. There it was.
Apple changed the links & runs exactly 2 copies of extension gallery in different domains.
Not working: https://safari-extensions.apple.com/
Working: https://extensions.apple.com/
They have added "safari-" prefix, but that site is not working.
When you click it from menubar or settings. you go the first one which is not working.
Try the second.

Thanks 🙂

Yep- the tab <> space bar solution works well.

Bit of QA Apple? Just sayin'

Perfect, Thank you so much - that was very easy and works for me - hopefully apple will change the direction just to the working url: https://extensions.apple.com/

That would safe much effort and trouble so many already had with this issue.

OMG. Thank you thank you thank you. That is so simple, and phenomenally careless on Apple's part. What is their problem???

For the record, I will mention that this problem happens not only on El Capitan, but also on Yosemite with Safari 9. At the top of the "bad" Extensions Gallery page, I see this lovely message:

Extensions in this gallery are compatible with Safari 9.0 or later on OS X El Capitan or Yosemite. Please upgrade to
OS X El Capitan which includes Safari 9.0, or update to OS X Yosemite 10.10.5 and install Safari 9.0 from the Mac App Store.

Well, I'm running 10.10.5 and Safari 9.0.3. Clearly, something is wrong in either Safari 9 or the safari-extensions.apple.com page that is preventing the page from correctly identifying the OS and browser. (This message also pops up if you visit the Extensions Gallery in a browser other than Safari 9 or on an OS other than Yosemite or El Capitan.) It's clearly not simply a problem with El Capitan's new security features.

Hopefully this extra info can help bring about a more permanent fix from Apple.

worked for me

thx:)

Thank you for figuring this out. I am going to share this on the LastPass plugin support page as well. Tons of people wondering and I bet this will help more than a few of them as it did me.

Thanks! This works for me!

- open Keychain Access

- select the category "Certificates"

- go through all certificates in all of your keychains and check if they are still valid

- there are some with that are revoked or invalid

- DELETE them

Thank you (and @akawe) for putting me on the right track. This is it. It’s not an expired certificate that is wreaking havoc, but one whose issuer is no longer recognized and which is replaced with a newer one in the System Roots keychain. Somehow, it ended in the login keychain, probably because it was downloaded as part of cert chain for some website at some point in the past.

The fix is to delete the “VeriSign Class 3 Public Primary Certification Authority - G5” certificate from your login keychain to make Apple sites show the green EV certificate and the extensions gallery starts working.

THANK YOU. That was it for me!

Being on the other side of the Atlantic does not spare us from Apple's 'Forked-tongue' applications.

Fortunately this forum delivered, but not in quite the sequence that I've seen here.

For me it was a mix of two steps 1) Start in safe mode 2) Start Safari, select Safari > Preferences > Get extensions. Now manually edit 'Safari-' out of the URL address. I then noted that green coloured text 'apple inc' (as in AKAWE's reply: Dec 15) had replaced the deleted 'Safari-'.

I was now able to select the 'install now' text, which had now appeared.

The unique symptom that I oberserved here was that if I edited the URL in normal mode, it would immediately reset when I tried to enter. I needed the safe mode for the URL edit to work.

The: VeriSign Class 3 Public Primary Certification Authority - G5 deletion solved my problem of the vanished install button...

Thank you!

My client with brand new iMac and El Capitan can't install ScamZapper extension. Works on my Mac and El Capitan. No expired certs. No verisign cert at all. Safari extensions page shows green lock and Apple Inc. before the URL. We added Adblock Plus as a test. ScamZapper is from an unidentified developer. Tried the tab and space bar shortcuts in the trust window. Still doesn't install. iCloud keychain was off, we turned it on, same thing. Tried putting the ScamZapper.safariextz in ~/Library/Safari/Extensions/ and it was ignored. So we've tried everything. Only thing we didn't do... the iMac came with 10.11.4 and we let the App Store Software Update install the delta update to 10.11.5. So we could try the combo updater. Shot in the dark, but I'm out of ideas. Anybody?

Update: Combo update did not help. Safe Boot did allow the Safari extension to be loaded, and it stuck when rebooted normally. So something that loads optionally with the system blocked the installation.

yes! this really helped!