Synfony application in Google compute engine

I am trying to migrate a symfony/php application from AWS to Google cloud (compute engine).

I have trasfered all AWS RDS mysql databases to Google cloud SQL, and I have also created a new CentOS 7 VM instance (withing a group and a Load Balancer) to host the symfony application.

After setting up all the required environment for symfony to work, I have managed to get the application running but when I login in the main page, I receive an error: Error 101: Ajax Call Failed.

Ans also, when I try to retrieve some records from a table in mysql (I have verified that table is ok via mysql client access), I get the following error: DataTables warning (table id = 'example'): DataTables warning: JSON data from server could not be parsed. This is caused by a JSON formatting error.

I have checked all PHP, mysql, symfony, json rpms and are all properly installed.

Any help or advice would be much appreciated. Also, I have not found any relevant guide for installing a synfony application in Google compute engine with autoscale and load balancing in mind (I have only managed to find it for Amazon AWS)

Thanks,

George