[atlas] Atlas probe offline

My Atlas probe (ID 14587) has been showing as offline since December 
16th.  I can see DHCP requests/replies, it ARPs for the gateway and I 
can see DNS requests and pings from the probe, and successful replies to 
all of this traffic being sent back to the probe.  e.g.:

12:13:38.790096 IP 192.168.0.115.35404 > 217.146.115.154.53: 2+ AAAA? 
ctr-nue15.atlas.ripe.net. (42)
12:13:38.797337 IP 217.146.115.154.53 > 192.168.0.115.35404: 2 1/6/12 
AAAA 2a01:4f8:120:14ee::2 (482)
12:13:38.798179 IP 192.168.0.115.57785 > 217.146.115.154.53: 3+ A? 
ctr-nue15.atlas.ripe.net. (42)
12:13:38.799649 IP 217.146.115.154.53 > 192.168.0.115.57785: 3 1/6/12 A 
78.46.87.51 (470)
12:14:58.990977 IP 192.168.0.115.37934 > 217.146.115.154.53: 2+ AAAA? 
IUSB-READONLY.U36.M6466B3B0EC98.sos.atlas.ripe.net. (68)
12:14:59.060132 IP 217.146.115.154.53 > 192.168.0.115.37934: 2 1/1/2 
AAAA 2001:67c:2e8:11::c100:1337 (164)
12:14:59.060983 IP 192.168.0.115.57523 > 217.146.115.154.53: 3+ A? 
IUSB-READONLY.U36.M6466B3B0EC98.sos.atlas.ripe.net. (68)
12:14:59.114915 IP 217.146.115.154.53 > 192.168.0.115.57523: 3 1/1/2 A 
193.0.19.55 (152)
12:14:59.115925 IP 192.168.0.115 > 193.0.19.55: ICMP echo request, id 
954, seq 0, length 64
12:14:59.142586 IP 193.0.19.55 > 192.168.0.115: ICMP echo reply, id 954, 
seq 0, length 64
12:15:00.116800 IP 192.168.0.115 > 193.0.19.55: ICMP echo request, id 
954, seq 1, length 64
12:15:00.143773 IP 193.0.19.55 > 192.168.0.115: ICMP echo reply, id 954, 
seq 1, length 64


I can't see any other IPv4 traffic, but I do see IPv6 HTTPS traffic. 
I'm not sure where to go next with figuring out why the probe seems to 
have vanished.  Any ideas would be greatly appreciated.

Many thanks.

-- 
  - Steve