Could you provide more details on what you mean by it crashes?
Are you using a free ssl certificate provider?
Sounds like possibly your certificate is getting expired and needs to be renewed. If your certificate is only valid for a month make sure to renew your certificate before the current one expires. Some providers allow this to be automated.
I wouldn't recommend you put the setting off even if you have a certificate installed, customers may still be able to access you store through insecure methods.
403 forbidden can be an NTFS permissions issue on the underlying file system. Usually, the user account under which the IIS App Pool (for your particular website) is running, does not have modify permissions on the NopCommerce folder. problem may occur when adding/removing plugins, as nopcommerce app will try to modify installedplugins.json and not have NTFS permissions to modify the file.
Hopefully your hosting provider can assist in this area, or you are able to view/edit permissions in hosting control panel