Appending data to a CSV file within a flask app

Hi! As seen in the title, I can't seem to add/append data or text to the csv that I have uploaded to my flask app that is being deployed in Google Cloud Run. But when I try it locally using Jupyter Notebook, it seems to work just fine. 

Here is the code:

#load the csv
features = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
url_data = pd.read_csv("RetrainDatabase.csv",low_memory=False)

#append the new data features
url_data.loc[len(url_data )] = features

#save the new csv
url_data.to_csv("RetrainDatabase_V2.csv", index=False)

/r/flask
https://redd.it/13fcehr