This function is related to the NX series recorders and is due to the "Removes FTP function" on the NX series recorders in April 2022.

*Notes on n3r file download function in WV-ASM300
To download n3r file from a recorder of this version or later:

　・WV-ASM300 needs to be upgrade to version 4.00 or later
　・Set [n3r file download method (NX series)] to "Extension" on the [Basic setup] tab of WV-ASM300

Also, there is the explanation in operating instructions of ASM300.
https://i-pro.com/products_and_solutions/sites/default/files/2023-03/PGQP2679BAJ1_WV-ASM300_OI_en.pdf
3.2. Settings relating to the system
3.2.1. Basic setup
n3r file download method (NX series)