Flagged, challenged, or blocked — and guessing at the cause burns time and IPs. Work these seven steps in order to find the real reason and fix the right layer.
Diagnose before you fix. Retry the request from a known-clean mobile IP: if it works, the cause was IP reputation (ASN, subnet, or a blocklist) — switch IP type. If it's still blocked, it's your fingerprint or behavior. If a real browser on a clean IP is still refused, the site is enforcing a policy(identify or pay), not detecting you. The seven steps below isolate which.
The fastest signal. Success means the original IP's reputation was the cause — stop here and switch IP type.
If it resolves to a hosting/cloud provider (AWS, OVH, DigitalOcean), the ASN is the giveaway. Datacenter ASNs are flagged by default.
A clean IP in a dirty /24 still inherits suspicion. If the neighborhood is burned, rotating within it won't help.
See whether the IP appears on DNSBLs or fraud-score vendors. If it does, it is presumed guilty regardless of your behavior.
An instant 403 before any JS runs points at a TLS/JA4 or headless mismatch — not the IP. Drive a real browser engine.
CAPTCHA loops on a clean IP often mean robotic timing or request cadence. Add jitter, respect rate limits, vary navigation.
The site wants identification (Web Bot Auth) or payment (pay-per-crawl), not just detection. Decide whether to identify, pay, or move on.
Most flags resolve at steps 1-4 — the IP layer. That's the whole thesis of the IP reputation guide: reputation gates everything, so a high-reputation IP fixes the majority of "why am I flagged" cases outright.
Usually the IP's reputation degraded: it (or its subnet) accumulated abuse, landed on a fraud feed, or the target tightened its rules. Less often, your fingerprint or request pattern changed. Diagnose by testing the same request from a known-clean mobile IP — if that works, the original IP's reputation was the problem.
Rarely worth it. Reputation recovers slowly and you do not control the blocklists. The practical fix is to move to a high-reputation IP (real mobile or clean residential) rather than rehabilitate a burned one. For mobile IPs, rotating to a fresh carrier IP is instant and effectively gives you a clean address.
Isolate one variable at a time. Same request + clean mobile IP that succeeds = it was IP reputation. Still blocked from a clean IP = fingerprint or behavior. Still blocked with a real browser on a clean IP = the site is enforcing a policy (it wants identification or payment), not just detecting you.
Real 4G/5G mobile + residential IPs across 17+ countries — $4/GB, free endpoints, free rotation to a fresh clean IP.