Hi There, 

Starting this thread as directed by @Clive_A  here Wrong and no icon after firmware upgrade SG2210P v5.20 - Business Community (tp-link.com).

I have now, on three separate occasions, upgraded my TL-SG2218 Version 1 switch from firmware v1.1.8 to v1.20.0 as prompted by the Omada Controller (OC200), and on all three occasions have been left with an unusable network. Manually downgrading back to 1.1.8 fixes the problem. I have tried various troubleshooting steps, but as the network is generally unusable it is difficult to know what to do next, and to be honest the grief I get from the rest of the house when it is down means I don't have much time!

Given that there are not huge reports of this, I wonder if it is something with my configuration that is causing an issue with the new firmware. 

Network Setup.

I am using an OPNSense Router with the TL-SG2218 connected to it. Connected to the TL-SG2218, I have an OC200 Controller, multiple TL-SG2008 switches, 3 EAP610 APs (via the TL-SG2008 Switches), along with a few directly connected devices (Media Box, Camera NVR, Windows PC). The TL-SG2008 switches upgraded to the new firmware v4.20.0 (from v4.0.7) with no issues as far as I can see. Omada OC200 controller is on the latest offered firmware (5.12.9 / 1.26.3 Build 20230906 Rel.36269). The OPNSense router provides DHCP, DNS, and is configured with the VLANS. The switches have the OPNSense router set as the gateway for the VLAN interfaces. Management is at Default LAN/Vlan Tag 1. 

I have configured various VLANs, and an external Freedradius server - all working with no issue with the current setup. As soon as I upgrade the TL-SG2218 to v1.20.0 I get connectivity problems - difficult to nail down, but I cannot connect to local devices, no internet access. I do appear to get an IP as expected - the issue appears to be DNS related, perhaps? ALL devices on my network report a lack of internet connectivity - whether that be those devices directly connected to the switch, those connected via the TL-SG2008's, or Wireless devices connected to the EAPs. I have persisted for over an hour on one occasion checking configurations, rebooting my router, re-setting and re-adopting the TL-SG2218 with no luck. The only thing that fixes the issue is rolling back the firmware.The Omada controller does see, and can manage the switch. 

Any thoughts? I can provide the device data *.zip privately (on 1.1.8 firmware) if that may provide some clues to a configuration issue, or otherwise?

The only other oddity I have on the network is one of my TL-SG2008 switches has a 'Solid' system LED, rather than flashing. It works, can be seen and is managed by the Omada Controller, but the manual suggests this means it is in an abnormal state? I have checked the configuration and nothing seems amiss - the same as my other switches with flashing system LED's. 

Thanks,