Question Dual channel RAM problem on Dell Optiplex 5055 ?

[Bober kobryn]

my brother bought a Dell Optiplex 5055 with these specs:
Ryzen 5 1500 Pro,
2 x Hynix DDR4, 8GB, 2400MHz
MB Dell 0P03DX

The RAM was inserted into slots A2 and B2. In the bios it shows that they work in dual channel but in CPU-Z it shows single channel. When I change RAM to slots A1 and B1 I have a black screen and the orange LED is flashing. Is it possible to run RAM in dual channel mode on this motherboard or is it still working in single channel ?

 

[Bob.B]

my brother bought a Dell Optiplex 5055 with these specs:
Ryzen 5 1500 Pro,
2 x Hynix DDR4, 8GB, 2400MHz
MB Dell 0P03DX

The RAM was inserted into slots A2 and B2. In the bios it shows that they work in dual channel but in CPU-Z it shows single channel. When I change RAM to slots A1 and B1 I have a black screen and the orange LED is flashing. Is it possible to run RAM in dual channel mode on this motherboard or is it still working in single channel ?

Put the ram in A2+B2.
Show a screenshot from cpuz that shows single channel.