Just for the sake of argument, have you tried any of these ideas?
- Format the drive with OPL (simply try to access it in OPL and it will auto-format it if it's not formatted) - then re-format it in wLaunchELF
- Try setting jumpers to Cable Select
- Try removing all jumpers
The first one actually worked for me with a drive that wouldn't recognize at all in wLaunchELF HDD Manager.
the 2nd & 3rd options we things i've had to do to get finnicky HDDs to work in a PC that wouldn't detect properly. May not help at all on PS2 but won't hurt to try if OPL doesn't fix it for you.
Honestly if you don't mind spending some money I would get the SATA conversion PCB for your network adapter and then you can use up to a 2TB SATA HDD or SSD in 3.5" or 2.5". I realize that's not the solution you asked for but who doesn't want 2TB of games in their PS2?