I was having issues with this the other day but solved my own issue.
For those who are having an issue logging on the multi-player launcher and have mcafee there is an easy fix. If it is currently installed be sure to check the “quarantined items” first to be sure no FAF related items are there. If you choose to reinstall do not launch until doing the next step.
Under PC Security (under settings) go to Real-Time Scanning and add three files as exceptions that are in the FAF Client/lib section.
These three files are:
uid.exe
faf-ice-adapter.exe
FAF-UID.EXE
After doing this, there should no longer be any issues.