What's your network topology? Generally we don't connect the switch as " switch1----switch2----switch3----switch4----switch5----switch6", it will increase broadcast domain and network burden. In my...

If you want to configure the switch through Port28 on VLAN99, you need to set up the PVID of Port28 to 99.

It's abnormal that TL-SG3210 doesn't show the green icon on the web. It represents that the SFP module doesn't work on the switch. Maybe you can try to force the SFP port to 1000M speed and FULL...

After you configure LAG, all Layer 2 feature will generate an entry of LAG, include VLAN, STP, IGMP Snooping and so on. I think you can check the configuration of VLAN. You also need to click the...

You need to click Save Config after configuring. Otherwise the settings will be lose after rebooting.

Telnet or SSH also failed? Maybe the Switch's IP has been changed and could you confirm that you didn't use DHCP to get IP address on the switch? If you cannot access the CLI interface, I don't know...