You will need to run the below as Administrator , if the use doesn’t have local admin you will need to change them to one then remove after  ;

• Right-click on the Outlook shortcut holding the SHIFT key and choose Run as administrator
• Go to File > Options > Trust Center > Programmatic Access
• Set the programmatic access to Never warn me about suspicious activity (not recommended)

IMPORTANT NOTE: If these option are greyed out, it usually means that you didn’t run Outlook with administrative rights.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Outlook\Security
DWORD: ObjectModelGuard
Value: 2

As an alternative way, you can achieve the same result by altering your registry file in the following way:

• Navigate through HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\15.0\Outlook\Security  (create the key if it doesn’t exist)
• Add the following DWORD item:
  • CheckAdminSettings , with a value of 1.
  • AdminSecurityMode , with a value of 3.
  • PromptSimpleMAPISend , with a value of 2.
  • PromptSimpleMAPINameResolve , with a value of 2.
  • PromptSimpleMAPIOpenMessage , with a value of 2.
  • PromptOOMCustomAction , with a value of 2.
  • PromptOOMSend , with a value of 2.
  • PromptOOMAddressBookAccess , with a value of 2.
  • PromptOOMAddressInformationAccess , with a value of 2.
  • PromptOOMMeetingTaskRequestResponse , with a value of 2.
• Navigate through HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\outlook\security  (create the key if it doesn’t exist)
• Add the following DWORD items:
  • CheckAdminSettings , with a value of 1.
  • AdminSecurityMode , with a value of 3.
  • PromptSimpleMAPISend , with a value of 2.
  • PromptSimpleMAPINameResolve , with a value of 2.
  • PromptSimpleMAPIOpenMessage , with a value of 2.
  • PromptOOMCustomAction , with a value of 2.
  • PromptOOMSend , with a value of 2.
  • PromptOOMAddressBookAccess , with a value of 2.
  • PromptOOMAddressInformationAccess , with a value of 2.
  • PromptOOMMeetingTaskRequestResponse , with a value of 2.