PC not starting after adding new M.2 SSD

Hello @ESChestnut

try changing the 3rd SSD sata port,

because some actual signal routes are shared between here and there, read your motherboard's manual more more carefully and you will notice some place has small prints, if you use port 1 then can't use port 5, etc etc.....

i.e. my x370 taichi M2.socket2 cannot be used together PCIe_slot5, because they are both wired together as one or the other.

Hello,

Good to hear your keyboard is working and able to enter BIOS. Previously sounded like you can't enter bios after adding 3rd SSD = Crucial P3 1TB

No idea what's going on your side.

May be if you tell more accurately what you plug in and what not plug in, your description is quite confusing.

Hello @ESChestnut

OK, let's see if I understand correctly.

Old OK state was: -
A) Sata_SSD_1_brand_A_capacity_X in socket sata_1 with OS windows version ???
B) Sata_SSD_2_brand_B_capacity_Y in socket sata_2 without OS just for data
C) M.2 socket is not occupied

I suspect MBR partition type is used in A) is this true? please confirm back.

See MBR vs. GPT = https://www.freecodecamp.org/news/mbr-vs-gpt-whats-the-difference-between-an-mbr-partition-and-a-gpt-partition-solved/#:~:text=As%20MBR%20is%20older%2C%20it's,is%20starting%20to%20catch%20up.

MBR vs. GPT is important because there's a BOOT setting that calls for only GPT
- and will not boot MBR (i.e. your old Sata_SSD),
-- which I suspect your NVMe_SSD_3_Crucial_P3_1TB in socket M.2 is GPT.
--- but no, if you've not even managed to boot, hence not yet format the P3_1TB, hence no yet have GPT nor MBR???? please confirm back.

In order to boot GPT partition format, must disable CSM something something or NO legacy something something, forgot what exactly sorry, it's one of those things when you look at the UEFI you'll know ah ha that one....

Hence when you
>remove A) Sata_SSD_1_brand_A_capacity_X in socket sata_1 with OS windows version ???
and
>remove B) Sata_SSD_2_brand_B_capacity_Y in socket sata_2 without OS just for data
and
>plug_in C) M.2 socket alone wtih NVMe_SSD_3_Crucial_P3_1TB
it cannot boot ....
---- but no, wait, if you've not even managed to boot once with C), means you haven't even transfer OS from A) to C)

hmmmmm, MBR or GPT worst case is can't boot,
----- but UEFI bios will show the Crucial_P3_1TB exists.......
-------- and the problem is you can't even enter UEFI bios with it .......
possible last conclusion it is defective dead or arrival DOA, please plug the Crucial_P3_1TB into another computer to check.

Sorr to hear @ESChestnut

Most likely now, very very possible last conclusion it is defective dead or arrival DOA, please plug the Crucial_P3_1TB into another computer to check.

Is there a BIOS update or previous version that can be restored that it may work with?