Using the minmax function in conjunction with the repeat function is exactly what this challenge describes, but this was not inherently obvious to me at first. The way to pass this challenge is to remove the max-width value within the repeat function, and then add the minmax function in place of the repeat max-width value.
Here is an example of what that looks like using a before and after approach:
grid-template-columns: repeat(3, 1fr);
grid-template-columns: repeat(3, minmax(50px, 2fr));