T140 Memory Upgrade - Population Error

Hi Everyone, I hope you can help me!

I am trying to upgrade the memory of my T140 server and every memory I try results in the Memory population error. I have flashed the bios and idrac to the latest versions and tried the following memory:

Currently installed is 1x 8gb chip - 8GB PC4-2666V-ED2-11

I first tried, but later found out that 32gb chips are not supported: 

Timetec 64GB KIT(2x32GB) DDR4 2666MHz PC4-21300 Non-ECC Unbuffered 1.2V CL19 2Rx8 Dual Rank 288 Pin UDIMM Desktop PC Computer Memory RAM Module Upgrade (64GB KIT(2x32GB))

Then I tried:

Timetec 32GB KIT(2x16GB) DDR4 2666MHz PC4-21300 Non-ECC Unbuffered 1.2V CL19 2Rx8 Dual Rank 288 Pin UDIMM Desktop Memory RAM Module Upgrade (32GB KIT(2x16GB))

but regardless, the only chip that works is the original 8gb - can anyone point me in the right direction please?

Thanks

Matt