Here is the link:

NOTE: For Macs running Mac OS 10.15.6, once you've installed the above VMware Horizon program, you will need to make a slight adjustment. In the top bar select the program name, Preferences, Security, and select a button that states: 'Do not verify identities.'

WINDOWS 10 & 8.1 USERS:If your CAC a 'GEMALTO TOP DL GX4144,' 'GEMALTO DLGX4-A 144,' 'Oberthur ID One 128 v5.5 Dual', 'Oberthur ID One 128 v5.5a D' or 'G&D FIPS 201 SCE 3.2' or 'G+D FIPS 201 SCE 7.0' you 'may' be able to use your CAC without needing to install ActivClient.

Read more about the older CACs and how to replace them

Here are more options for you (if the above didn't work)

ACTIVCLIENT INSTALLATION PROBLEMS AND SOLUTIONS

Air Force users, download Lotus forms from:
Download 'AFDPO Releases Updated IBM Lotus Viewer_DSign_3.5.1.333.exe' under Software link
OTHER AIR FORCE SPECIFIC PROBLEMS:
Problem 1: Receiving 'Your CA was not recognized. You should contact your CSA/LAN support team for assistance with DoD certs on this computer. You can install the latest DoD certs from...' error message when attempting to access the AF Portal
Information:The Cross Cert remover tool removes certificates which cause the cross-certificate chaining issue from Microsoft Local Computer and User Certificate stores. This will prevent your certificate from appearing to be issued by roots other than DoD Root CA 2 and being denied access to DoD websites. Some computers may have the Federal Bridge Certificate Authority's DoD Root CA 2 certificate installed. This conflicts with the DoD's DoD Root CA 2. You must remove the DoD Root CA 2 signed by the DoD Intermediate Root CA 1 in order to use the AF Portal with your CAC.
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Cure 1-1: Follow the guidance in this PDF, slide 15 has download links for the Cross Cert remover tool.
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Cure 1-2: If [after following guidance above] you're still having problems, go from this direct link: https://www.my.af.mil
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Problem 2: Air Force users receiving 'There was a problem with this browser accessing your CAC for authentication. You may have pressed 'cancel' button in your browser's certificate selection prompt. If you are trying to authenticate with your CAC, please clear your SSL sessions. In IE go to the Tools-Internet options. Select the content tab and press the 'Clear SSL State button.' If this does not work or you are unable to complete this close all open browser windows and try again.
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Force Quit App Mac

Cure 2-1: Verify your clock settings on your computer. One person's battery had died, and his clock was set for November 2011, when it was actually August 2012.
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Problem 3: Air Force users seeing strange error message when using Outlook Web Access 2003 with Internet Explorer 10 or 11
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Cure 3-1: See here for solution.
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Problem 4: Air Force users with OS X 10.9.x Mavericks and newer having problems accessing https://leave.af.mil or https://www.my.af.mil/leavewebprod/login follow same guidance as DTS users via the DTS page.

Force Quit On A Mac

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How To Download Mac Update

Problem 5: Air Force webmail constantly getting the message The page cannot be displayed
Cure 5-1: Follow this guide to find out how to add https://*.mail.us.af.mil to your trusted sites
INFORMATION FOR APPLE MAC USERS ONLY
NOTE: In order to access some of the Air Force CAC-enabled websites, you must CANCEL when it first asks for your PIN. After canceling, then choose your certificate, it will give you a second opportunity to enter your PIN. NOW enter your PIN.
Information for Air Force personnel using Apple Computers: AROWS will not continue to the login page if it identifies your browser as non-compatible. This is easily fixed by having Safari report it 'is' IE. Go to Safari->Preferences ->Advanced and ensure the 'Show develop menu' check box is ticked. Now when you open NROWS and it gives the browser error, go to the Develop menu in the menu bar and select User Agent->Internet Explorer (any version 6.0 or greater) The 'Unsupported' page will refresh, Now paste the URL below back into the web browser again, you should be back at the login screen. This should work from the air Force Portal, or directly at the URL: https://arowsr.afrc.af.mil/arows-r
Try using User-Agent Switcher for Chrome
You can try this as well for AROWS, but, you'll need Google Chrome:
NROWS sets some narrow parameters when it comes to User Agent identification. Thursby software has figured this out. You'll need to build an AppleScript and use Google Chrome as your browser:
The first step is to build the AppleScript.
  1. Open Utilities > AppleScript Editor.
  2. Paste the code from below.
  3. Choose File > Save As…
  4. Select File Format: Application.
  5. Give the item a name and save.
  6. Then run the app.
Code:
set myURL to 'https://arowsr.afrc.af.mil/arows-r'

tell application 'System Events'
set processList to name of every process
end tell
if processList contains 'Google Chrome' then
beep
set theReturnedItems to (display dialog 'Google Chrome is already running.' & return & 'Would you like to quit and relaunch it?' default button 'Cancel')
set theButtonName to the button returned of theReturnedItems
-- If user clicks 'Cancel', this part of the script is never executed.
end if
-- This gets the path to Google Chrome. Unfortunately, it also launches the app.
set myGoogleChromePath to POSIX path of (path to application 'Google Chrome')
tell application 'Google Chrome' to quit
delay 1
set myCommand to 'open ' & quoted form of (myGoogleChromePath)
set myAgent to '--args -user-agent='Mozilla/5.0 (X11; U; Linux x86_64; pl-PL; rv:2.0) Gecko/20110307 Firefox/4.0'
set myscript to myCommand & ' ' & myAgent & ' ' & myURL
do shell script myscript
Safari keeps crashing
An Air Force person emailed this fix to me: He would load his OWA, and the window would only stay open for about 10-20 seconds before OWA tried to open a calendar popup reminder. This popup would crash his Safari window, leading him to a frustrating 'Safari quite unexpectedly' error message. He could access other CAC websites like Air Force Portal, DTS, Leaveweb, and ADLS. He found a workaround while searching through Thursby forum that had the idea of going to Options, Accessibility, selecting Use the blind and low vision experience. This disabled the annoying calendar popup, now his OWA window no longer crashes Safari. He mentioned the visual experience is more basic now, but at least he can access his email.