When I attempt to update the template for t3.nano (I also tried t2.nano) I get the error that I am not authorized from AWS. I have tried this several time and am sure I selected the proper EC2 config when creating a new template.
Thanks for sharing the screenshots, I am not sure of this error but you are using latest version t2.nano. Please we are restricted only to use t3.nano. Could you follow the instructions in part 6, uncheck only the box in 6.1.4 and choose t3.nano from the dropdown.
In the second screenshot I had the same issue and use reset to launch template. Then try to update again. Thanks