My Streaming Stick+ is also in use on a Samsung, most likely a different model. I have occasional loss of wifi connection, but have always been able to get it back via:
Settings > System > System restart
(Or for Roku TV: Settings > System > Power > System restart)
These things are just little special purpose computers. Like their big brothers sometimes you just need to clear things out by restarting them.
If a restart doesn't do it, try pulling the power plug to the device for a minute or so then plugging it back in.
Also, sometimes the tv itself can interfere with wifi reception with a stick plugged directly into the TV's HDMI port. If there are other available HDMI ports you can try moving to one of them to see if it helps. Roku also has a free HDMI extender available for Roku Sticks that can move your stick a few inches away from the port - you can order one here. But it's nothing more than an HDMI extension cable with a male HDMI plug on one end and a female socket on the other. If you don't want to wait for shipment from Roku you can probably find one locally in several different lengths.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you.
Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X | Streaming Stick 3600
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