Connected, no internet

I just bought a Netgear R7800 and updated to the latest firmware v1.0.2.28. I have Optimum cable service and a wifi issue with android devices. I also have a Windows10 tablet that initially says "Connected - No Internet" but then it works fine after a few seconds. However, the android tablet and smartphones barely connect no matter what I try. My two PCs that are hardwired work perfectly.

It happens on both 2.4 and 5g