TL;DR

Receiving "General Error" when attempting to upgrade OC200 controller firmware via Controller>Maintenance>Check for upgrade

While my expectation is the upgrade should work using the check for upgrade function, I considered I may need to do a manual firmware update for the controller.  However as I note below pertaining to the hardware version, I'm afraid I might select the incorrect hardware version on the TP-Link site, as there are both v2.0 and v.2.6.  

Therefore, which would I choose? Do I simply choose the hardware version as shown on the device label only?

And, would it be recommended to update each one in order rather than jump to the latest as there are six updates following the current firmware installed?  

The other devices were able to check and advise there is new firmware available from the Devices menu.

This is new equipment just purchased and I have only just set this system up, everything is working well for the past week and WAN and LANs are accessible; but now I need to update firmware of devices.  However, I wanted to update the controller before updating any other devices as that seemed most intuitive to do.

Thank you for your guidance!

Topology:

• Controller (hardware) - PoE powered from switch
  • OC200 v2.0 (as shown on controller maintenance page)
  • Hardware version: I'm somewhat confused on hardware version though, because on the controller info page it shows 2.0 but on the device label it shows OC200(UN) ver 2.6.  Additionally, in this form for the post, only V2 is available.
  • Controller version 5.6.4
  • Firmware 2.6.1 Build 20220921 Rel.35903

• Router
  • ER605 v2.0 (as shown on controller devices page)
  • Hardware version: Again, somewhat confused on hardware version, the device info pane shows 2.0 but the device label shows ER605(UN) ver 2.6
  • Firmware 2.1.2 Build 20230210 Rel.62992

• Switch
  • SG2210MP v4.20 (as shown on controller devices page)
  • Hardware version: Again, the device info pane shows 4.20 but the device label shows SG2210MP ver 4.26
  • Firmware 4.20.0 Build 20230818 Rel.72032

• AP - PoE powered from switch
  • EAP670(US) v2.0 (as shown on controller devices page)
  • Hardware version: Once again, the device info pane shows 2.0 but the device label shows EAP670(US) ver 2.6
  • Firmware 1.0.0 Build 20230918 Rel. 55839