@PaoloG75 See if this post helps. Make sure to check the two links in the "Recommended Troubleshooting" section

@David-TP

@iplr See if this post helps if not please get back to us https://www.tp-link.com/us/support/faq/2925/

@jagSparrow The following was taken from this post post where other users were having the same issue "Currently, some users have confirmed that restarting the ISP modem again after enabling the Guest...

@xcybermail Because your running your decos in AP mode you lose out on a bunch of options including "Device Isolation" that's why you are unable to find this option. Here is a list of what options...

@HomeNetwork123 See if this helps https://www.tp-link.com/us/support/faq/3297/#:~:text=Open%20the%20Deco%20app%2C%20go,part%20of%20the%20internal%20antennas.