Per chance are you using Google Chrome when access the AF portal? If so, can you access it successfully with another browser?
Is your Mac running any AntiVirus software? If so, disable or remove them, and then, try accessing this portal again.
Typically, this error is associated to attempting to access a secured website using HTTPS/SSL. You may also see an error message of something like: "Your Connection is Not Private" or the "Connection is Not Secure."
If you are using Chrome, here's something you can try to resolve this:
- Try accessing the portal again as you normally would.
- Click on the HTTPS lock icon, and then, select Details.
- Select View Certificate.
- Select Details in the Certificate viewer, and then, select the top certificate. (It should be from an address other than the one you are trying to access.)
- Select Export and save the certificate file.
- Go to Chrome Settings > Advanced > Manage Certificates
- Select Import, and then, select the certificate that you just exported.
- Restart Chrome