Issues connecting more devices to WiFi

I had connected a lot of devices to the WiFi, more than 40 with no issues (mainly KASA light switches). Now I'm in a point where I can not add any additional device to the WiFi. I had tried removing one device and I was able to connect the new device but the old one not able to connect. Also some connected device like a google assistant, my iPad and one TV sometimes disconnects and reconnects by themselves. Currently Tried to add new KASA light switches and not able to do that. what Can I do? Is there a limitation of number of WiFi devices connected to my Network?