Hello @Squeezy ,

Welcome to our community.

Let me address both parts of your question:

Why the TL-PA411 may not be connecting

Powerline adapters work by sending data signals through your existing electrical wiring. Even if the building shares electricity from the main house system, the connection between the two buildings may pass through separate electrical phases, isolation transformers, or sub-panels — any of which can block or severely degrade the powerline signal. The long cable run and multiple outdoor outlets along the way can also introduce interference.

Before assuming the circuit is the problem, here are some troubleshooting steps worth trying:
1. Make sure both adapters are plugged directly into wall outlets (not power strips or extension cords).
2. Reset both powerline devices and re-pair them. (Reset guide: https://www.tp-link.com/support/faq/312/)
3. Try pairing them using the tpPLC Utility: https://www.tp-link.com/support/faq/1615/
4. Ensure both adapters are on the latest firmware, then attempt pairing again. (Firmware upgrade guide: https://www.tp-link.com/support/faq/1614/)

Would a fiber or a more powerful adapter help?

Unfortunately, your internet speed (whether ADSL at 50Mbps or fiber at 8Gbps) has no effect on whether powerline adapters can communicate through the electrical wiring. The powerline signal travels independently of your internet service. So switching to fiber would not resolve the pairing issue.

A more powerful (higher-spec) adapter could potentially offer a stronger signal, but if the electrical circuit between the two buildings has isolation or phase separation, even a high-end adapter is unlikely to bridge that gap reliably. The circuit compatibility is the fundamental factor here.

If you've tried the troubleshooting steps above and the adapters still won't connect, it's likely a circuit incompatibility issue between the house and the outbuilding. In that case, alternative solutions such as a long Ethernet cable run, MoCA adapters (if coaxial cable is available), or a point-to-point wireless bridge may be more reliable options for your setup.

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