I’ve run the Wi-Fi analyzer and changed channels multiple times and still have an issue at random times on random devices where the device can’t get an IP from the router, I must add I have a TPLink extender in another room but it’s set to no DHCP as I actually only connect 2 devices to it.
Other things that I would try (in no particular order):
- Ensure that both devices are running the latest available firmware.
- Factory reset both the DLink and TP link routers and set everything up again.
- Check whether a device connected to one of the ethernet ports on the dlink is able to access the internet even when the wifi appears to have failed. This will highlight whether the problem is limited to wifi devices or whether it is caused by other connectivity problems.
- Try using the google dns (8.8.8.8 and 8.8.4.4) instead of the dns settings supplied by your isp. Restart your router/client devices so that it forces them to obtain and use the revised settings.
- Switch off the extender to try and isolate whether the Dlink's wifi problem persists when it is the only access point.
- If possible setup the extender (or another router/AP) as a dumb access point by connecting the lan port on the extender or another router/access point to the lan port on the dlink. Disable wifi on the dlink and change the lan ip of the extender to be one of the ip addresses outside of the dlink's dhcp pool. Set the default gateway on the dumb AP device to the ip address of the main router e.g. 192.168.1.1. This assumes that the wired network can still access the internet.
- Check on the web interface of the TPlink extender whether it is able to pick up a strong signal from the Dlink. An extender should be positioned midway between the main router and where you want to the signal to be extended to. It should not be placed at the remote location where you want the signal to be extended to since it will suffer from the same interference problems created by neighboring networks. If the extender is connected using ethernet cable then you can place it at the remote location since there will be no transmission losses on the network cable.
- Look at placement of both the Dlink and TPLink. Try putting both devices in open areas without nearby obstacles and raise them off the floor. Antennas must be in the vertical position as this will cause the wifi signal to travel further.
- Check that your isp does not block the router's mac address in an attempt to force usage of their router.
- Buy a second hand router/access point on FB marketplace/Gumtree. There appears to be an over supply of unused routers that nobody wants and you should be able to find one close to you for relatively cheap. Check the specs for something that preferably supports gigabit networking and mu-mimo wifi N/AC support. Mu-mimo allows multiple clients to stream data at the same time without having to wait on each other.
