Subnet, network, host and possibly other tabs are not shown
I speculate that this is a regression after the most recent Primeng/Angular upgrade.
Open a tab with a list of subnets. Click on one of the subnets. The subnet contents are shown and the tab with the list of subnets is unselected, but the tab for the subnet is not visible. In other words, you always have only one (default) tab and no way to navigate between different tabs.
In the following picture you can see what happens after clicking on a subnet. The subnet contents are displayed but there is only one tab.