Hi,
According to this [https://www.crucial.com/compatible-upgrade-for/dell/xps-l401x|supplier] they guarantee that their 2TB SSDs will work so it appears that there is no limitation on the motherboard.
As the SSD is not being detected in BIOS, did your SSD come with a [https://www.connection.com/product/edge-7mm-to-9.5mm-solid-state-drive-spacer-adapter-for-2.5-drives/pe247270/31499932|7mm to 9.5mm adapter]? (supplier example only)
The adapter is designed to hold a 7mm SSD (which yours is) in the correct position in a 9.5mm drive bay (which your laptop has) so that there is good contact between the SSD and the sata connector in the laptop