Buffalo TS-RHTGL-R5 User Manual page 6

After your TeraStation has completed booting up, check the
LINK/ACT LED on the front of the TeraStation. If it's lit, then
your TeraStation is connected properly, and you can go on
to page 8. If it's not lit, turn to page 7 for troubleshooting.
Press the power button on the front panel. LEDs will light
as your TeraStation boots up.

TeraStation Quick Setup