I am getting the same error on my both WordPress sites:
Your content folder in "/home/{my_user}/public_html/wp-content/uploads" is not writeable.
They both are hosting on a dedicated service using WHM.
I changed the permission on the ../uploads/ folder to 777 and it works but I don't think this is a valid exercise. The current setting on the folder is 775
Can you please give me some steps to diagnose this one?