the problem is that the Apache log messages are self-explanatory. Access is being denied based on one or more (obsolete) Allow/Deny directives in either a .htaccess file or in the main Apache configuration. Check your .htaccess files and make sure none of them have Allow/Deny directives that are denying access to legitimate files/users. If you can’t find any, then contact your hosting company again and request that they remove all global Allow/Deny directives for your account.
Your hosting company should have known this.
Let me know when you contacted your host provider, what they said!
If you have more questions, feel free to ask!