Streaming stick stuck on bouncing Roku logo

Try a different power source.  If you're using the TV's USB port to power the stick, try the supplied USB power adapter.  If you're already doing that, try a different one that can supply at least 1 Amp (1000mA).  After that, a factory reset is about all that's left.

How do I factory reset my Roku® streaming device? | Official Roku Support