If your custom domain's CNAME was proxied through Cloudflare (the orange cloud), Cloudflare answers DNS with its own edge IPs and hides the record Suga checks for. Verification would fail with a generic "CNAME not found" message, with no hint that the proxy was the cause.
Suga now detects when a record is being proxied through Cloudflare and tells you exactly what to fix: set the CNAME to "DNS only" (the gray cloud), then verify. No more guessing why an otherwise correct record won't validate.