Some devices will not connect to WiFi.

I have been having an issue for the last few months where some devices will not connect to my WiFi. 2 iPad pros will basically never connect, some smart switches and cameras occasionally lose connection temporarily, a few cameras won’t ever connect, and my wife’s phone won’t ever connect. We have a tp link deco mesh system and pay for 1gig internet. Speed test on my phone throughout the house give good results, over 400mbps in all areas. Tesla would not connect today and gave this error.

I have also reset the network and got a new modem. What could my issue be?