Hello Strummer62, thanks for joining the NUC Community
Before replacing the units I think it will be necessary to test at least one of the memory listed on the compatibility list tested peripherals.
You can also try the troubleshooting provided on this link. Intel® NUC — Troubleshooting No Boot Issues
In addition you may want to check this other thread Re: NUC D54250WYKH not booting (Memory Socket problem?)