You didn't mention which OS you're running..... if it's Windows 10, the AMD drivers are broken including SLS (Eyefinity):
From the latest 15.201.2401 driver documentation:
"this driver has general support for Windows 10 for listed Workstations products. The driver is not recommended for full advanced workstation features ... We recommend NOT to upgrade to Win 10 if you are using advanced workstation features.)...CF Dual, CF Tri/Quad, Display Overlap, Display Overlap Post Processing, EDID/MST, Framelock/ Genlock, SLS, MGPU-SLS, Stereo (Display based, Passive), 10 bit(native, packed pixel, SLS), SDI Custom timing, Stereo (Active, Auto) are NOT currently supported."
Also, outside of Windows 10 issue, I think 4x1 landscape is supported but not 4x1 portrait.... but not sure.
Please provide exact info on your monitors, cables, adapters, OS, driver installed......