Hey, I met this same issue long time ago with differnet model. Consult tplink and they said we can take the hardware version on the label as the right one. Therefore, your TL-MR6400 should be V1....

Generally speaking, the home led should be on which means they are working properly. Can you still get itnernet through the unit? If not, you may need to repair them. Of course, if internet...

Is it wireless router mode? How about restart the device? if you still can't edit it, it's better to send email at support@tp-link.com with your screenshot and HW & FW version of TL-WR940N.

Do other smart phone works properly? After you updating the iOS version, you get this error? Try to reinstall the kasa app.

How do you get into that link? If we need to creat a cloud kasa cloud account, we can directly do it with kasa app. You may refer to this link: https://www.tp-link.com/us/faq-948.html

Do you mean that camera won't get it power on after the power gets back? Or it will lose all the configuration once it powered off?