Unable to Share Folder

I am a user under an enterprise account but when I log in and create a form, I am unable to share it with other users.

I checked your account and it looks like your account is the sub-user for a Silver account.  I did not see an Enterprise account associated with organization.  In terms of sharing forms, the feature is only available to accounts that had used the feature prior to October 2018.

https://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User

Their account has used the feature previously so it is still enabled, the feature is not enabled for your specific account.