Cannot change the wifi setting of doorbell E340

I try to change my wifi setting for my doorbell, but it keeps saying cannot connect. Then, I tried to delete it and adding it again. Still cannot connect to my new wifi.

I tried to add the device to my old wifi router, it connected. But when I changed the wifi setting for my new router, it failed to connect again. Now, I tried an hour, but it cant connect to the old wifi router nor the new one.
It’s literal a torture. I spent a day just want to switch to the new wifi router.

Sorry to hear that, I hate it when something so simple doesn’t work. Ugh.

Well, for the heck of it… go into your routers settings and turn off the 5 GHz band and if you have 6 also turn that off. You can turn them back on later.

Remove the device doorbell from the app.
Now do a reset to the doorbell.

Add the doorbell to the app and perform the normal setup and see if you can connect to your new router 2.4 GHz.
Good luck