User Profile Service Connections Blank

More than likely you applied a CU, but at the moment I am not able to determine what causes this to occur.

UPS Connections Query Empty (After CU is applied)

Grant Local Administrator Privileges to Database Access Account (on the machine hosting the UPSA)
Reboot Server
Start User Profile Service Application (in Central Admin)

After synchronization is done, remove the Database Access Account from the Local Administrators group and reboot.