Have you used the same cables (outputs/inputs) on the same monitors/tv?
I had amd hd6870 which supported five 24" displays but only when I used DVI-D, HDMI and 3 mini-DP outputs in exactly one configuration, If I used DVI-D on one particular monitor, 5 display config worked, If i used DP on it, it didn't. No logical explanation as it had DVI-D, DP and HDMI inputs and they all worked in single configuration, but not with 5 displays.
I've learned that multi monitor display setups beyond 3 screens, can be tricky, when using only one GPU. It's easier to buy 2 low power GPUs like GTX 1050/ti or RX 550/560 to avoid troubles. Or you could go with Maxtor/Quadro/FirePro line, but they are rip-offs if you ask me (except if you need their video editing capabilities).