Spent an hour figuring this out tonight, maybe this will save you some time.
I have an RCA universal remote model RCRN03BR and an Insignia 55″ TV model NS-55df710na19
The remote seemed to have lost its code memory and wouldn’t work again so needed to be reprogrammed.
I tried all the auto code searches but kept getting almost but not quite there. I ended up trying all the Insignia 5 digit codes and found one that seemed to work okay.
12049
(hold down the TV button while typing in the 5 digit code) the remote should work as expected.
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