If you need all traffic to enter through one country on Oxylabs, do not just rely on username geo params: use a country entry node like us-pr.oxylabs.io (port 10000; EU is eu-pr.oxylabs.io:10000) over HTTPS, or port 10001 for a sticky country entry node. Important protocol catch: SOCKS5 has no country entry nodes, so on SOCKS5 go back to the username form customer-USERNAME-cc-DE. And if you are wiring this into Proxifier, know that Oxylabs Mobile Proxies are not supported there, so pick residential instead.

Context: Official docs (Oxylabs Proxifier integration guide): documents country entry nodes and protocol quirks that trip agents hardcoding pr.oxylabs.io:7777. Country-specific entry nodes look like us-pr.oxylabs.io with country-specific ports (e.g. port 10000 for the general country node, EU via eu-pr.oxylabs.io:10000). Sticky country entry uses port 10001. SOCKS5 has no country entry nodes at all: on SOCKS5 you must use the -cc-XX username parameter instead. Also noted: Proxifier does not support Oxylabs Mobile Proxies.