I have a CRS305-1G-4S-1N. I can get to RouterOS no problem after I do a cold reset @ 192.168.88.1. I have tried everything I could find or think of to get to the SwOS with no luck.
I went to System/RouterBOARD/Settings and changed BootOS to SwOS after which I cannot get to the SwOS web page after a reboot.
I tried Ethernet and SFP+ ports. Checked the DHCP leases and it never picks up an IP. Tried 192.168.88.2. Activity light is on. Winbox was no help as it is just a mirror of the RouterOS page.
Factory Firmware 6.45.1
Current Firmware 6.45.1
Upgrade firmware 7.2.3
Tried updating firmware, same issue.
If I set the BootOS to SwOS in Winbox, after reboot, just goes back to RouterOS
Are there any commands I can use from the RouterOS Terminal window?
I need SwOS in my application as a spare SFP+ switch.

Why would you choose SwOS if you can use RouterOS?

Did you set a fixed IP address (i.e. 192.168.88.2) on the client to connect to SwOS (192.168.88.1)?
Think by default there is no DHCP client active.

Correct - the client PC needs to be set static for initial config of a SwitchOS devices as there is no DHCP server in SwitchOS. The switch should default to 192.168.88.1.

Is the switch plugged into your network where it can get a DHCP address?

If I remember correctly I was bitten by this and spent several hours trying to figure out why my pings to the 192.168.88.1 address would work, then quit.

Apparently the default behavior is to use the 192.168.88.1 as a fall back if DHCP is not available. If it is, it will pull and address from your DHCP pool.

It depends on which version of SwitchOS. Sorry, my memory is not remembering the details, but it's in the doc files. It changed a few revisions ago. As I recall, it used to be static only and now you can set it for DHCP, but as I recall (don't hold me to this) that default is static to 192.168.88.1. Check the docs.