What's the firmware version of your D7? Is it up to date?
Only Andoid wireless clients and wired PCs are working properly all the time, right?
There are some aceess points connected to LAN port of D7?
Can you update your iPad and iPhone? Are they connected to 2.4GHz band or 5GHz band?

What's the firmware version of your D7? Is it up to date? [COLOR=#ff8c00] Updated to the most current because of issues
Only Android wireless clients and wired PCs are working properly all the time, right? Correct
There are some access points connected to LAN port of D7? Correct. These will not allow access either
Can you update your iPad and iPhone? Are they connected to 2.4GHz band or 5GHz band? Both Bands. This is a public area so no control over updates

I seem to be having similar behavior on a brand new C7 with a slight variant. Android fine. No PCs.
Newer ipads and Macbook pro retina with 802.11ac ok, older ipads and Macbook pro retina without ac have intermittent access.
A router reboot fixes the access problems for these older devices for a while. The router gives the
older devices DHCP address and can see them fine, but packets don't seem to make it from the router to the internet.
Problem seems to happen on both the 5Ghz and 2.4Ghz bands.

I have now placed a second unit with another customer (I bought two units not knowing about this issue) after a week they are complaining about the same issue on their IPhone's. and IPad's. We have left this device on the old firmware.
TP Link haven't got back to us in over 3 weeks regarding this issue. Customer support 0%, our TP-link spend last year 9K.

So, I found the problem on my C7. Your mileage may vary.

In Security/Advanced you can enable/disable DoS Protection.

The default values in this are way too low, and at intermittent times they trip, causing the
router to lock out the ipad/phone or whatever device caused the trip.

To confirm you've been locked out: in that same screen, hit the 'Blocked DoS Host List' button
to see that your device has been blocked.

To fix: either disable the DoS entirely or put in values that are much higher.
Not that the values are not total packets, but a rate of packet production.

One poster elsewhere in this forum noted that this DoS protection is exactly backwards.
You'd want to disable the address from which the packets are coming, not the target address (e.g. your device.)

Thanks for that BoulderCO.

Both units have DoS Protection off by default.
I have now added the unit back on to the network as a router rather than a modem router to see how this effects things. I have 2 additional wireless AP plugged into it still.
Straight away 1 IPhone on IOS6 was unable to connect wirelessly.

I will need to see what is reported over the next few days.

I have a similar problem and it is not limited to iOS devices as per other posts I've seen, both my wife's and my own Android phones drop out for no reason occasionally. They remain connected to the wifi but there is no internet connectivity while at the same time, other devices such the iPad (which this has also happened to) continue to function normally.

But currently it's worse than that, my laptop cannot connect to the wifi at all, and for no apparent reason. I am writing this from my laptop but to do so I had to start up my phone's wifi hotspot and connect to that instead, which proves it is not a problem with the laptop's network adapter.

Had a multitude of stability problems before upgrading latest firmware (Archer_D7_V1_150824) but still see things like this. There is no DoS setting under security on the latest firmware that I could see. Beginning to feel like I have a faulty device. Time to contact support, although from what I have read on the forums I'm not confident in getting a resolution quickly.

I Have had a reply from Lizzy @ support with this suggestion:
login change ssid name > channel 6 > change to 20mhz > advanced uncheck WMM > save reboot

Giving it a try

I will be interested if this gets solvedI'm having the same problem with the tp link w9980 Sometimes my iPhone can receive data from the Internet and other times it will not yet it always picks up the wifi signal My Windows 7 machine is fine However i have noticed that my windows 10 machine has a similar problem and the only way to correct it and get data from the Internet is by re booting the router/ modem