WYSE 5070 extra RAM

We are starting to see a lot of popups indicating the Thin Clients are running out of RAM.

Looking online we have purchased a number of 4Gb SO-DIMM 260 2400MHz.

However the Thin Clients aren't seeing them, with either one or two sticks.

Orange lights comes on, then changes to solid white.

I've also tried 2133Ghz RAM, and seeing the same.

The 5070 manual says, the orange should flash if they is an issue (have tried with no RAM and indeed it flashes).

are the 5070's fussy on the memory brands, we have tried Crucial, Integral, 2-Power

Cheers

Michael