It's default enabled on downstream for all lines(if the modem supports it). Was there any work done to your line the day it removed G.INP? Or did you change package/provider? It's usually only removed with a DLM reset or product change. After that it's roughly 10-15 days till it comes back on. I have no idea what will happen with your line though as I don't recall such an occurrence.
I was not aware that any work was done on my line on the day that it removed G.INP. I haven't changed package or provider either. Just an update, G.INP returned last Wednesday (25th Jan) at 5-6am in the morning.
Stats recorded 31 Jan 2017 00:00:49
DSLAM/MSAN type: BDCM:0xa48c / v0xa48c
Modem/router firmware: AnnexA version - A2pv6F039v.d26a
DSL mode: VDSL2 Profile 17a
Status: Showtime
Uptime: 5 days 18 hours 17 min 42 sec
Resyncs: 0 (since 30 Jan 2017 23:57:16)
Downstream Upstream
Line attenuation (dB): 13.7 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 76167 20000
SNR margin (dB): 6.4 6.1
Power (dBm): 13.0 5.1
Interleave depth: 8 1
INP: 48.00 0
G.INP: Enabled Not enabled
Vectoring status: 5 (VECT_UNCONFIGURED)
RSCorr/RS (%): 0.0060 0.9287
RSUnCorr/RS (%): 0.0000 0.0000
ES/hour: 0 0