L4D2 Workshop - Failed to Publish File! Error Code: 2

[EvilWalrus]

I'm trying to get into the modding community. Anyways I tried uploaded a sound mod that edits the credit song. I tested it out before trying to publish it, and it worked as expected. The .vpk file size is 49.69 MB. I looked all over the internet and I can't find an answer. Other people have had this problem, but no one quite knows the solution. Any help would be appreciated. Thanks!