Hey there!
It seems this ISP in particular isn’t peering with Cloudflare anymore! A few months ago (not sure the exact date) I was getting routed though GRU node (Sao Paulo) but now I’m always getting routed to MIA node (Miami) instead.
IPv4:
fl=17f59
h=[redacted]
ip=179.176.57.xxx
ts=1542831871.572
visit_scheme=http
uag=Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0
colo=MIA
spdy=off
http=http/1.1
loc=BR
tls=off
sni=off
IPv6:
fl=17f74
h=[redacted]
ip=2804:7f1:2080:3a00:1d5e:xxxx:xxxx:xxxx
ts=1542832544.026
visit_scheme=http
uag=Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0
colo=MIA
spdy=off
http=http/1.1
loc=BR
tls=off
sni=off
Testing from another ISP, TIM (4G), seems to be routing properly to GRU on both IPv4 and IPv6.