check your code implementation for moving average forecast.
Also remember this assignment doesn’t require you to use everywhere len function which is a common mistake by most learners. You need to use the SPLIT TIME correctly as per instructions mentions you to find time_series.
Sharing a linked comment which provides an overall debug points from all the grade function codes, see if it helps.
Also the most usual issue would be either hard coding the path, using incorrect variables(global instead of local or vice-versa) or using incorrect functions.
Regards
DP