Hello  @meirbit 

Thank you for the feedback, can I know the model and OS of your 2 laptops and failed to connect to Wi-Fi? 

If only extender failed to get IP address from range extender

1. Ensure range extender is on the latest firmware 

https://www.tp-link.com/support/download/tl-wa850re/v6/#Firmware

2. Remove Wi-Fi profile or forget extender Wi-Fi on that certain device and reconnect to Wi-Fi of extender 

 Remove Wi-Fi profile on Windows

How to remove existing wireless network profile on Android & iPhone

3. Try some suggestions in Case 4: Certain Device Unable to Connect Wi-Fi extender & Case 5 

  @meirbit 

Glad to hear from you again.

Do you mean 1)  Extender itself not working and all devices lose internet  or 2)  only two of the network devices Dell & Lenovo can not connect to it while other devices still able to connect to range extender? 

For 1) How about the Led Status on your TL-WA850RE right now?  If the Signal led goes off, that means Range extender lost Wifi of router, you could reset and reinstall the extender again. Please verify the wifi password as instructed here before reinstallation. 

TP-Link Range Extender Setup (Range Extender Mode)

For 2) If only Dell& Lenovo failed to obtain IP:  You could try case5, to manually turn on DHCP server on the range extender and setup an IP address for it within router's IP range

 Case 5 : PS4 / IOS devices fail to connect to RE's Wi-Fi network or failed to get an IP address