I had no issues adding this item to ArcGIS Online, with the option checked to publish as a Hosted Feature Layer, and then adding the layer to a Web Map. Guide here:
What error message are you receiving?
If you are using a public account, you may need to have a user licence for ArcGIS Online that lets you create content. If this is a non-commercial project an ArcGIS for Personal Use licence has a low annual fee - I have one for personal projects and it's great.
I managed to load the file after few attempts. Not sure what was the problem.
I made my map and saved it but now i have an error saying that the layer is not responding.
Any idea what the problem is ?