GCloud – App Deploy Error: Internal Error Occurred

I am new on gcloud apps, need help on deployment web apps.

I created an App Engine and a Cloud SQL for MYSQL, it is in a different project.
Let's call App Engine as web1 and sql as mysql1.

When I deployed web1 using "gcloud app deploy app.yaml", the upload process was success but when in the process "Updating service" it turns with error "ERROR: (gcloud.app.deploy) Error Response: [13] An internal error occurred"

Here is with the full error

Updating service [default]…⠶DEBUG: Operation
[apps/and-web-test/operations/f7c36da5-de76-436d-9e71-785d549273e0]
complete. Result: {

"metadata": {
    "target": "apps/and-web-test/services/default/versions/and-web-mm-001", 
    "method": "google.appengine.v1.Versions.CreateVersion", 
    "user": "xxxxxxxxx@gmail.com", 
    "insertTime": "2019-07-25T04:54:53.630Z", 
    "endTime": "2019-07-25T04:55:11.386Z", 
    "@type": "type.googleapis.com/google.appengine.v1.OperationMetadataV1"
}, 
"done": true, 
"name": "apps/and-web-test/operations/f7c36da5-de76-436d-9e71-785d549273e0", 
"error": {
    "message": "An internal error occurred.", 
    "code": 13
} }

Is it because my script has a bug or something else that i need to setup like permission on the Cloud SQL project?