QNAP have identified a number of design differences and compatibility issues with different brands of NVMe PCIe and M.2 solid state drives. To protect your data, NVMe PCIe/M.2 SSDs can no longer be used to create new storage pools or static volumes in QTS 4.3.4.
Only creating new storage space is prohibited. If are you already using NVMe PCIe/M.2 SSDs for data storage, then your existing storage configuration will be unaffected after upgrading to QTS 4.3.4.
You can still use M.2. SSDs for storage by inserting them into internal M.2. slots, or by adding a QM2 expansion card to your NAS. For more information about QM2 cards, see www.qnap.com/en/accessories.