Every few minutes windows status bar will show a yellow triangle to indicate that there is a problem with the network. Indeed the guest is no longer able to connect to the internet. I click on devices - network and shared network (even though it's ticked already) and the error will disappear for a short while. If I go through the Windows troubleshooting it says it can fix it and the problem does go away for a few minutes but eventually returns. I am using a MacBook Pro 2017 with a wifi connection. This problem is most irritating. The host MacOS High Sierra 10.13.4 does not experience any network problems itself.
Kindly start the virtual machine and go to the top menu bar, click on Actions--> Configure--> Hardware--> Network1--> change the source to Bridge network ( Default adapter) and check if it helps.
It depends upon the connection you use like wired or wireless ( refer https://bit.ly/2IyqSWj for more information )