This issue is caused by the wrong Secuirty Network Zone.
You can edit the "Serverconf.xml" to solve this issue.
If you need make your ACC to public, change <SecurityZone> to "true".
Here is a smaple for your reference.
<securityZone allowDebug="true" allowHTTP="true" allowSQLInjection="true" label="Public Network"
name="public">