...

1. With the Wi-Fi to Ethernet adapter powered on, use a small screw driver (or pen, pin, paper clip etc.) to press and hold the RESET button (small hole adjacent to the Ethernet port) until the entire ring of blue lights illuminate briefly (approximately 8 seconds).

2. Release the RESET button and wait the Wi-Fi to Ethernet adapter to reboot to its factory default settings.

Appendix: TP-Link user guide

https://static.tp-link.com/2020/202004/20200422/1910012794_TL-WA850RE_UG_REV7.0.1.pdf