@Gin83 

When resetting the HS103, do a full reset by holding the side button for 20 seconds. 

If your router has a guest network, try enabling that to see if it connects that way.

@Tony that did not work. Any other ideas? 

@Gin83 

I would recommend reaching out to support to see if there may be an issue with the plugs themselves. 

In other cases, users have changed their wireless security from WPA/WPA2 to WPA2 got their plugs connected. 

I am having the same issue with configuring a HS103 v2 plug that used to work, was sitting on a shelf for a while and now I am setting it up for a different purpose. Nothing in the network HW or config has changed. Android Play Store reviews note similar issues with TP Link connectivity. Are we getting a fix for the app any time soon?

I have done multiple factory resets, network is WPA2 and 2.4GHz only.

Edit: Fixed it, kind of! So I tried a few older versions of Kasa app for Android. A version from this year's summer did not work either. Version "Kasa Smart 2.17.0.892" from Nov 11 2019 works! It actually has a selection for HS103 specifically. The new app does not have this. The connection and pairing works great. The Kasa app prompted for smart plug FW update, and the plug still works after that. I then uninstalled the old app, installed latest, and the plug is still available and works great after I log into my account. TPlink. Your SW is broken. Please fix it.