You need 2000 Light on your weapon to finish soul attunement. The first picture was with the value of light set at 1999. It is obviously not enough.

Light Values (All Confirmed 100%):

Feeble: 1 (Confirmed)
Gentle: 2 (Confirmed)
Bright: 4 (Confirmed)
Brilliant: 6 (Confirmed)
Blinding: 12 (Confirmed)
Newborn Star: 16 (Confirmed)

Tiers:

'No Activity': 0 - 199
'Indisctinct Activity': 200-399
'Faint Activity': 400-599
'Slight Activity': 600-799
'Modest Activity': 800-999
'Distinct Activity': 1000-1199
'Robust Activity': 1200-1399
'Vigorous Activity': 1400-1599
'Intense Activity': 1600-1799
'Extreme Activity': 1800-1999
'Bursting Activity': 2000+ (Complete)

Notice : I released a simple app that allows you to check the status of your Novus weapons. That said, I cannot post it here (to my knowledge). You can head over to BlueGartr or guildwork and find it pretty easily.

Light Values By Event:

FATE | Base : Feeble, Bonus: None(?)
Wolve's Den | Base : Feeble, Bonus: Gentle
Map (Alexandrite) | Base: Gentle, Bonus: None(?)
Turn 4 | Base: Gentle, Bonus: Bright
Primal (HM) | Base: Gentle, Bonus: Bright
Primal (EX) | Base: Bright, Bonus: Brilliant
Turn 1, 2, 5 | Base: Bright, Bonus: Brilliant
High Roulette | Base: Bright, Bonus: Brilliant
Expert Roulette | Base : Brilliant, Bonus: Blinding
Frontlines | Base: Brilliant, Bonus: Blinding
Second Coil | Base: Blinding, Bonus: None(?)
Syrcus Tower | Base : Blinding, Bonus: Newborn Star