Echoing that I noticed this became a problem sometime after launch as well. Hopefully they fix it soon; really sucks seeing those white numbers even though I'm locked on to a weak point.
Converse with fellow players
OK so this appears to be resolved. I'm not sure if it's related but I equipped the weapon and went out and killed things with them for a bit then when I came back to town I was able to do the potential upgrades.
Still very strange as my alliance members have confirmed they did not have to use a weapon before maxing out it's potentials. Maybe something for SEGA to look into anyway.
I can't seem to upgrade this set of daggers past the first potential. I keep getting the connection error message even though I am not using any modifiers and I was able to add augments and enhance the weapon to level 40. I have not yet tried to see if I can add potential to anything else but I'd rather not waste the materials. Is anyone else having this issue?