To put it more directly: you
must reset your PowerBox to
no configuration and then use WinBox to connect and perform basic configuration. Which includes:
- set a quality password for administrator's account
- create a bridge
- add all ether interfaces as bridge ports ... one by one (not by selecting "all")
- configure IP on bridge interface for management access ... either by setting IP address (don't forget to include subnet mask, e.g. 192.168.88.42/24) or by running DHCP client bound to bridge interface
- optionally any other necessary settings, such as adding default route (in case of static IP address assignment), adding NTP client settings, etc.
- ... and refrain from using QuickSet part of any UI at all times, it'll mess with your settings
After that, ether1 will be just the same as the rest of ports from network point of view (and management access as well).
BTW, if your cable is indeed Cat5 (without 'e' at the end, i.e. Cat5e), then it's only good for 100Mbps (might support 1Gbps on short distances, not on half of specced range) ... check any of numerous articleas about different UTP cable categories, e.g.
this one.
[edit] Cat5 cable should be fine, PowerBox is 100Mbps only in any case