This message was posted on behalf of Intel Corporation
Based on the description of the situation you are having, we can confirm that this is most likely related to a limitation on the motherboard or configuration issue.
From that third PCIe slot, do you have any other device connected in the M2P_32G?
We do suggest you updating the latest BIOS on your motherboard.
If this does not work, we recommend you to contact Gigabyte* and ask them if there are any settings that need to be changed, as we know the SSD does work fine.
About the other question you have, one of the main reasons why the Intel® Solid-State Drive Toolbox does not shows the update button is because of the missing NVMe* driver. You can try to install it from this link.
Let us know if you require further assistance.
Thanks, Nestor, will try it later.