App cannot create folder when needed, needs permissions
This  problem could be solved by deleting the "library" which is generated by Unity. Unity directory is as following:

Unity &gt;
- Assets
- Library &lt;- Delete the directory, and reopen Unity
- Log
- ProjectSettings
- Temp

On the other hand, you can see information about permissions and their errors in the following Apple website: https://support.apple.com/en-au/HT203538