When I sign up my account, this error appear "Connection error. Please try again in some time". How can I fix it?

[renjynusa]

Please help me, sir. When I sign up my account, this error appear "Connection error. Please try again in some time". How can I fix it?
error image:
https://drive.google.com/file/d/1tfwCQhRFVrD1UXYNRwP1f5VqtDJIsTu4/view?usp=sharing

[ssvas1997]

The current application which is in use has a proper sign up feature. It works fine when a user registers in the application. Please check for the errors by putting logs in the code. If still it persists just let me know.

[renjynusa]

it's say "This permission not allowed . You must enable this service in the console"

logcat when i sign up :

2019-10-23 21:04:47.718 800-800/com.example.hp.demo D/Name: renju
2019-10-23 21:04:47.802 800-800/com.example.hp.demo W/BiChannelGoogleApi: [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzal@4ba3794
2019-10-23 21:04:48.018 800-1192/com.example.hp.demo W/SyncTree: Listen at /userNames failed: DatabaseError: Permission denied

[ssvas1997]

Permissions in the firebase console must be enabled. Do refer firebase docs

[renjynusa]

how can i enable the permission in database ?

look like i have following the rule , and i still can't register/sign up
the log cat still say "Database Error : Permission Denied"

I only can login by adding manually email and password in firebase authentication
but can't sign up