Shelly EM Wi-Fi Connection Issue

[tiffy]

Having just migrated my FTTP, BT to Vodafone this week have been re-configuring my mostly Wi-Fi connected Home Assistant devices to the THG3000 Hub.
All successful with one exception, my Shelly EM (energy monitor) which for some reason refuses to connect to the main 2.4Gz Wi-Fi network, device is 2.4Gz only.
Even more strange, I can enable the guest network and it connects perfectly to this using the default "5" subnet?
Could live with this if I could change the guest subnet address to "0" which I use on the main network, changed from the default "1", hub won't permit this.

I have 2, Shelly-1 Relays on the system, these configure perfectly.
I can't believe that the Shelly EM is at fault as:
Connects with the temporary configuration, setup option.
Connects perfectly to the guest network.
Worked without issues on the BT SH-2 previously.

I know it's possible to use a third party router but that would be the last resort for me, just don't want the hassle of obtaining all the configuration details from VF especially as I have retained my digital LL which makes things more complex.

Anyone had similar issues?
Any suggestions appreciated. 

[Cynric]

@tiffy Can you see if the main WiFi is on channel 12 or 13 please? Some devices cannot use those channels. I did look at the Shelly website, but they have too many products and you didn't say which one.

[tiffy]

@Cynric  Many thanks for the reply, much appreciated.
In response, no, Wi-Fi channels 12 or 13 are not in use.
Would have thought that any channel anomalies would have equally applied to the guest network as well?
As stated, the device is a "Shelly-EM" (energy monitor) the basic, single phase device, has worked faultlessly for 2 years on my previous BT SH-2, results compiled on Home Assistant.

I never planned to use the guest Wi-Fi network but just through frustration enabled and tried a connection the Shelly-EM, was really surprised that it worked, provided an easy means to configure my desired (main) Wi-Fi details which I tried with and without IP address reservation, still wouldn't connect to main Wi-Fi network?
Have run out of ideas on this🤔

[Cynric]

@tiffy Unfortunately this kind of difference between the two WiFi provisions has been seen here before. It's odd, but I don't think that it has been explained yet.

[Jayach]

@tiffy 

Can you not use the device even though it's on the guest network?

[tiffy]

@JayachYes, I can access the Shelly-EM on the guest Wi-Fi but as previously mentioned they are on different subnets so will not integrate with all the other Home Assistant devices which are on my normal home network subnet address range☹️

Can see absolutely no reason why this device will connect via one Wi-Fi and not the other on the same router😕
In theory I suppose I could move all the Home Assistant Wi-Fi devices to the guest network, would be a lot of work, my Home Assistant server is ethernet connected which as such would have to stay on the router Local Network which has always to be on a different subnet range to the guest Wi-Fi network!!

[Ripshod · Accepted solution]

We've seen this before a few times. The fix is actually quite simple - let's see if I can explain it simply.

Disable the main wifi. Enable the guest wifi with the main wifi's ssid and password. Connect this Shelly device to the 2.4GHz band. Once it's connected disable the guest wifi and enable the main. Magically everything should connect now.

I've tried to do this from memory - maybe @Cynric has something to add (fill the gaps?)

[tiffy]

@RipshodMany thanks for the reply, much appreciated.
Just to clarify before I try this possible solution:
Do I need to change the guest Wi-Fi SSID to the same as the main Wi-Fi before trying?
I have just currently left the guest Wi-Fi SSID at default but previously changed the main Wi-Fi to the same SSID as my previous router (BT SH-2) in an attempt to simplify migration, this had worked with my previous Zen to BT migration.
The main & guest Wi-Fi passwords are already set to be the same.

[Ripshod]

If the Shelly unit is remembering the old SSID from BT then it may be refusing to connect because something strange (to it) has happened to the network (IP subnet, MAC etc). If this is the case you may have to completely reset the Shelly device.

In answer to your question: Disable the main wifi first, then activate the guest wifi the same ssid/password. You should see other devices reconnecting to the guest - this confirms the ssid and password are correct. 

[Cynric]

@Ripshod That sounds right to me.