Solved: Fix for "Apple Pay has been disabled because the security settings of this Mac were modified".

A restart was necessary for me as well. To be perfectly clear, here’s what I did:

• Open System Prefs → Software Update
• Click Advanced…
• Uncheck “Install system data files and security updates“ (all others checked)
• A dialog appears asking me to authorize w/Touch ID; do that
• Reboot
• System Prefs → Software Update → Advanced… again
• Recheck “Install system data files and security updates“ (all others still checked)
• Go to System Prefs → Wallet & Apple Pay
• Previously authorized cards now available again

Not sure if you have managed to resolve this since posting this, but I've had the same issue, nothing would resolve this issue. To save you spending hours on the phone like I did follow these steps

1. Ensure that your 'FIND MY' is turned off on your Mac
2. Turn your Mac off
3. Turn Mac back on and just before the apple logo appears hold 'COMMAND' and 'R'
4. This will take you to the MacOS Recovery screen
5. Log in to your account when it appears
6. Once logged on, go to the very top bar and select utilities
7. Click the startup security utility
8. This should then ask you for an administrators password, just your log in password as normal.
9. If your 'FIND MY' isn't turned off you won't be able to enter administrator's password
10. Once you are on that you need to select the highest security setting.
11. It will then give you a box to restart your Mac
12. Turn it back on as normal and try from there

Hopefully this will resolve it for you. I purchased my Mac secondhand and the previous owner had the security settings set to 'none', causing me the issues with adding my card.

This worked for me but I had to restart my laptop after unchecking the “install system data files and security updates” box and then check it again after it turned back on. Only then I was able to setup Apple Pay.

Thanks!!! I've been looking everywhere to figure this out. That box was unchecked on my Mac. So I checked it and went back to Wallet, clicked Add Card, and - voila - all my cards from my iPhone magically appeared. I was able to setup them up after verifying each. Apple Support did not even provide this resolution!

Thanks so much...

Thank you so much - mine was already unchecked so I checked it unchecked it then checked it again and it worked - so I unchecked it and it stopped working - so you must have it checked for Apple Pay to work.

This worked here on my MBP 16" as well.

It seems Apple really needs a refresh permissions feature across all devices as this is an ongoing problem with icloud things.

It did work for me too on a 2019 MacBook Pro 16-inch. Many thanks!

Thank you for posting this information. There have been a few cases of this and so far this is the solution. I added this information to a User Tip I created for Apple Pay issues - Problems and their solutions for Apple Pa… - Apple Community

Thank you! I just had to do this out of the blue on a years old fully upgraded and operational OSX 10.5.5 MBP! It was driving me nuts.

This worked for me as well. For me, though, the setting was disabled for some reason. I expect it might be due to the fact that I bought a new 16" MBP, and my old 15" 2015 MBP did not have the T2 security chip (or whatever it's called). So, if anyone is upgrading from an older model like me, you might find yourself in a similar situation.

Thanks for the tip, I would not have thought to look there!

WORKED GREAT!

I, just like you looked all around the web for a solution, until I came across your easy fix!

Thanks

It worked! Many thanks!!

Thank you. Totally solved that sticky ApplyPay issue on my Air.

This fix worked. Thanks.

thank you so much!! this has been driving me insane for months!