Gmail email in Outlook 2013

I have a client with a regular gmail email account (not corporate). They get their emails on three different devices - their Android phone and in Outlook 2013 on two different computers. Because they want to have the email on all three devices I have set up the accounts as POP rather than IMAP so that if they delete an email on one device it remains on the other devices. The phone appears to be working properly and does not affect the two computers with Outlook. However, If they get a new email and Outlook is open on computer #1 they receive it in the Inbox but when they open Outlook on computer #2 they do not get the email. The same happens if they first get the mail on computer #2 then they will not receive it on computer #1. Both computers are in the same location and behind the same router.  I have gone into their webmail gmail account and looked at the settings under "forwarding and POP download" and it is set to "keep gmail's copy in the inbox". Like wise in Outlook on both computers it is set to "leave a copy on the server" for 14 days.

I do not know where else to look to make any changes or why this is happening. Any help would be appreciated.

Thank you