I sent them a question but there has been no reply. I dug a bit deeper into their FAQ page and found this response:

18. Q. I have recently purchased a Big Button remote to go with an INSIGNIA TV. I cannot locate the code to use even when I go through the POWER SEARCH mode. Can you provide the correct code for me to enable the remote?
A. At the present time there is not a code for the INSIGNIA brand TVs and TV/VCR/DVD combo units. Since thousands of new electronic devices are added every year, we do the best we can to keep up with all the new models and try to add the codes in our upcoming versions of the remotes.
[Link: bigbuttonremotes.com]